THIS DATASET WAS LAST UPDATED AT 8:10 PM EASTERN ON MARCH 24
2019 had the most mass killings since at least the 1970s, according to the Associated Press/USA TODAY/Northeastern University Mass Killings Database.
In all, there were 45 mass killings, defined as when four or more people are killed excluding the perpetrator. Of those, 33 were mass shootings . This summer was especially violent, with three high-profile public mass shootings occurring in the span of just four weeks, leaving 38 killed and 66 injured.
A total of 229 people died in mass killings in 2019.
The AP's analysis found that more than 50% of the incidents were family annihilations, which is similar to prior years. Although they are far less common, the 9 public mass shootings during the year were the most deadly type of mass murder, resulting in 73 people's deaths, not including the assailants.
One-third of the offenders died at the scene of the killing or soon after, half from suicides.
The Associated Press/USA TODAY/Northeastern University Mass Killings database tracks all U.S. homicides since 2006 involving four or more people killed (not including the offender) over a short period of time (24 hours) regardless of weapon, location, victim-offender relationship or motive. The database includes information on these and other characteristics concerning the incidents, offenders, and victims.
The AP/USA TODAY/Northeastern database represents the most complete tracking of mass murders by the above definition currently available. Other efforts, such as the Gun Violence Archive or Everytown for Gun Safety may include events that do not meet our criteria, but a review of these sites and others indicates that this database contains every event that matches the definition, including some not tracked by other organizations.
This data will be updated periodically and can be used as an ongoing resource to help cover these events.
To get basic counts of incidents of mass killings and mass shootings by year nationwide, use these queries:
To get these counts just for your state:
Mass murder is defined as the intentional killing of four or more victims by any means within a 24-hour period, excluding the deaths of unborn children and the offender(s). The standard of four or more dead was initially set by the FBI.
This definition does not exclude cases based on method (e.g., shootings only), type or motivation (e.g., public only), victim-offender relationship (e.g., strangers only), or number of locations (e.g., one). The time frame of 24 hours was chosen to eliminate conflation with spree killers, who kill multiple victims in quick succession in different locations or incidents, and to satisfy the traditional requirement of occurring in a “single incident.”
Offenders who commit mass murder during a spree (before or after committing additional homicides) are included in the database, and all victims within seven days of the mass murder are included in the victim count. Negligent homicides related to driving under the influence or accidental fires are excluded due to the lack of offender intent. Only incidents occurring within the 50 states and Washington D.C. are considered.
Project researchers first identified potential incidents using the Federal Bureau of Investigation’s Supplementary Homicide Reports (SHR). Homicide incidents in the SHR were flagged as potential mass murder cases if four or more victims were reported on the same record, and the type of death was murder or non-negligent manslaughter.
Cases were subsequently verified utilizing media accounts, court documents, academic journal articles, books, and local law enforcement records obtained through Freedom of Information Act (FOIA) requests. Each data point was corroborated by multiple sources, which were compiled into a single document to assess the quality of information.
In case(s) of contradiction among sources, official law enforcement or court records were used, when available, followed by the most recent media or academic source.
Case information was subsequently compared with every other known mass murder database to ensure reliability and validity. Incidents listed in the SHR that could not be independently verified were excluded from the database.
Project researchers also conducted extensive searches for incidents not reported in the SHR during the time period, utilizing internet search engines, Lexis-Nexis, and Newspapers.com. Search terms include: [number] dead, [number] killed, [number] slain, [number] murdered, [number] homicide, mass murder, mass shooting, massacre, rampage, family killing, familicide, and arson murder. Offender, victim, and location names were also directly searched when available.
This project started at USA TODAY in 2012.
Contact AP Data Editor Justin Myers with questions, suggestions or comments about this dataset at jmyers@ap.org. The Northeastern University researcher working with AP and USA TODAY is Professor James Alan Fox, who can be reached at j.fox@northeastern.edu or 617-416-4400.
As of September 2024, California had the most mass shootings in the United States, with 26 total shootings since 1982. The source defines a mass shooting as a shooting where three or more people were killed. Recently, a mass shooting occurred in the state of Maine on October 26, 2023, during which one of the highest number of fatalities from a mass shooting was recorded after Robert Card opened fire in a bowling alley and a bar, killing 18 and injuring 13 others. Firearms in the U.S. Mass shootings in the United States are disturbingly common. In comparison with other Western countries, there are significantly more shootings in the U.S., which some theorize is due to the relatively lax gun control laws. Gun control laws in the U.S. are dependent on the state, and the right to own a firearm is enshrined in the United States Constitution. Mass shootings The worst mass shooting in the U.S. was the Las Vegas Strip massacre in 2017, which resulted in 58 deaths and 546 injuries. 13 of the worst mass shootings in the United States have occurred since 2015 and the vast majority of these incidents in the U.S. have been carried out by shooters who are White and male.
California reported the largest number of homicides to the FBI in 2023, at 1,929 for the year. Texas recorded the second-highest number of murders, with 1,845 for the year. Homicide victim demographics There were a total of 19,252 reported homicide cases in the U.S. in 2023. When looking at murder victims by gender and ethnicity, the vast majority were male, while just over half of the victims were Black or African American. In addition, homicide victims in the United States were found most likely to be between the ages of 20 and 34 years old, with the majority of victims aged between 17 to 54 years old. Are murders up? In short, no – since the 1990s the number of murders in the U.S. has decreased significantly. In 1990, the murder rate per 100,000 people stood at 9.4, and stood at 5.7 in 2023. It should be noted though that the number of homicides increased slightly from 2014 to 2017, although figures declined again in 2018 and 2019, before ticking up once more in 2020 and 2021. Despite this decline, when viewed in international comparison, the U.S. murder rate is still notably high. For example, the Canadian homicide rate stood at 1.94 in 2023, while the homicide rate in England and Wales was even lower.
In the period between 2023 and 2024, the risk of mass murder in Morocco stood at 1.2 percent. The risk decreased in comparison to the previous years observed, and in the same period, the country ranked 46th among 166 nations. Furthermore, there is no record of mass killing in Morocco since 1945. Overall, on the Global Peace Index, Morocco achieved a score of 1.97 in 2022. The indicator ranges from one to five, where the lower the score, the more peaceful the country.
Find data on deaths of Massachusetts residents. Information is obtained from death certificates received by the Registry of Vital Records and Statistics.
https://dataverse.harvard.edu/api/datasets/:persistentId/versions/2.0/customlicense?persistentId=doi:10.7910/DVN/PXUZShttps://dataverse.harvard.edu/api/datasets/:persistentId/versions/2.0/customlicense?persistentId=doi:10.7910/DVN/PXUZS
Petition subject: Execution case Original: http://nrs.harvard.edu/urn-3:FHCL:12208711 Date of creation: (unknown) Selected signatures:William SullivanCharles G. LoringHenry H. FullerDavid Lee ChildRalph Waldo EmersonHarrison Gray OtisSamuel E. Sewall Total signatures: 92 Legal voter signatures (males not identified as non-legal): 92 Female only signatures: No Identifications of signatories: citizens, some of whom were present as jurors or otherwise at the trial of William Roby for the murder of Maria Leonard, and others of whom have become acquainted with the principal facts in the case from other sources Prayer format was printed vs. manuscript: Manuscript Additional non-petition or unrelated documents available at archive: additional documents available Additional archivist notes: William Roby, Maria Leonard; many notes and lengthy statements next to signatures Location of the petition at the Massachusetts Archives of the Commonwealth: Governor Council Files, September 1, 1832, Case of William Roby Acknowledgements: Supported by the National Endowment for the Humanities (PW-5105612), Massachusetts Archives of the Commonwealth, Radcliffe Institute for Advanced Study at Harvard University, Center for American Political Studies at Harvard University, Institutional Development Initiative at Harvard University, and Harvard University Library.
As of September 4, eight people were killed in mass shootings in the United States in 2024. A total 1,159 victims were fatally injured during mass shootings in the United States between 1982 and September 4, 2024.
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Morocco MA: Intentional Homicides: Female: per 100,000 Female data was reported at 0.552 Ratio in 2015. This records an increase from the previous number of 0.386 Ratio for 2013. Morocco MA: Intentional Homicides: Female: per 100,000 Female data is updated yearly, averaging 0.359 Ratio from Dec 2009 (Median) to 2015, with 4 observations. The data reached an all-time high of 0.552 Ratio in 2015 and a record low of 0.326 Ratio in 2009. Morocco MA: Intentional Homicides: Female: per 100,000 Female data remains active status in CEIC and is reported by World Bank. The data is categorized under Global Database’s Morocco – Table MA.World Bank: Health Statistics. Intentional homicides, female are estimates of unlawful female homicides purposely inflicted as a result of domestic disputes, interpersonal violence, violent conflicts over land resources, intergang violence over turf or control, and predatory violence and killing by armed groups. Intentional homicide does not include all intentional killing; the difference is usually in the organization of the killing. Individuals or small groups usually commit homicide, whereas killing in armed conflict is usually committed by fairly cohesive groups of up to several hundred members and is thus usually excluded.; ; UN Office on Drugs and Crime's International Homicide Statistics database.; ;
0 (persons) in 2024.
In recent years, gun violence in the United States has become an alarmingly common occurrence. From 2016, there has been over 10,000 homicides by firearm in the U.S. each year and firearms have been found to make up the majority of murder weapons in the country by far, demonstrating increasing rates of gun violence occurring throughout the nation. As of 2025, Mississippi was the state with the highest gun violence rate per 100,000 residents in the United States, at 29.4 percent, followed by Louisiana, at 28.1 percent. In comparison, Massachusetts had a gun violence rate of 3.7 percent, the lowest out of all the states. The importance of gun laws Gun laws in the United States vary from state to state, which has been found to affect the differing rates of gun violence throughout the country. Fewer people die by gun violence in states where gun safety laws have been passed, while gun violence rates remain high in states where gun usage is easily permitted and even encouraged. In addition, some states suffer from high rates of gun violence despite having strong gun safety laws due to gun trafficking, as traffickers can distribute firearms illegally past state lines. The right to bear arms Despite evidence from other countries demonstrating that strict gun control measures reduce rates of gun violence, the United States has remained reluctant to enact gun control laws. This can largely be attributed to the Second Amendment of the Constitution, which states that citizens have the right to bear arms. Consequently, gun control has become a highly partisan issue in the U.S., with 80 percent of Democrats believing that it was more important to limit gun ownership while 74 percent of Republicans felt that it was more important to protect the right of Americans to own guns.
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List Price: 25.98
A Recommended Book from: New York Times * Publisher's Weekly * Kirkus * BookRiot * Booklist * Boston Globe * Goodreads * Town Country * Refinery29 * CrimeReads * Glamour
Dive into a tour de force of investigative reporting (Ron Chernow): a "searching, atmospheric and ultimately entrancing" (Patrick Radden Keefe) true crime narrative of an unsolved 1969 murder at Harvard and an "exhilarating and seductive" (Ariel Levy) narrative of obsession and love for a girl who dreamt of rising among men.
You have to remember, he reminded me, that Harvard is older than the U.S. government. You have to remember because Harvard doesn't let you forget.
1969: the height of counterculture and the year universities would seek to curb the unruly spectacle of student protest; the winter that Harvard University would begin the tumultuous process of merging with Radcliffe, its all-female sister school; and the year that Jane Britton, an ambitious twenty-three-year-old graduate student in Harvard's Anthropology Department and daughter of Radcliffe Vice President J. Boyd Britton, would be found bludgeoned to death in her Cambridge, Massachusetts apartment.
Forty years later, Becky Cooper a curious undergrad, will hear the first whispers of the story. In the first telling the body was nameless. The story was this: a Harvard student had had an affair with her professor, and the professor had murdered her in the Peabody Museum of Archaeology and Ethnology because she'd threatened to talk about the affair. Though the rumor proves false, the story that unfolds, one that Cooper will follow for ten years, is even more complex: a tale of gender inequality in academia, a 'cowboy culture' among empowered male elites, the silencing effect of institutions, and our compulsion to rewrite the stories of female victims.
We Keep the Dead Close is a memoir of mirrors, misogyny, and murder. It is at once a rumination on the violence and oppression that rules our revered institutions, a ghost story reflecting one young woman's past onto another's present, and a love story for a girl who was lost to history.
ISBN: 9781549141577 Published: November 10th, 2020 By: Becky Cooper Read by: Becky Cooper
©2020 O’Connell (P)2020 Hachette Audio
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License information was derived automatically
This data set contains Somerville crashes that occurred from May 2018 to present. Crash reports are completed when a motor vehicle crash occurs on a public way and involves at least one of the following: Any person is killed, any person is injured, or damage is in excess of $1,000 to any one vehicle or other property. Data does not include crashes that are under active investigation, nor those that occur on state roads, which are under the jurisdiction of the Massachusetts State Police. State crash data may be accessed on the Massachusetts Department of Transportation’s crash data portal, IMPACT.
This data set should be refreshed daily with data appearing with a one-month delay (e.g. crashes that occurred from 1/1 will appear on 2/1). If a daily update does not refresh, please email data@somervillema.gov.
https://dataverse.harvard.edu/api/datasets/:persistentId/versions/7.0/customlicense?persistentId=doi:10.7910/DVN/VGEYZFhttps://dataverse.harvard.edu/api/datasets/:persistentId/versions/7.0/customlicense?persistentId=doi:10.7910/DVN/VGEYZF
Petition subject: Imprisonment Original: http://nrs.harvard.edu/urn-3:FHCL:26855760 Date of creation: 1676-09-05 Petition location: [Boston] Selected signatures:William WannuckhowJoseph WannuckhowJohn Appamatakqueen Total signatures: 3 Males of color signatures: 3 Female only signatures: No Identifications of signatories: all prisoners at the barr, [males of color] Prayer format was printed vs. manuscript: Manuscript Native American tribe: Nipmuc Acknowledgements: Supported by the National Endowment for the Humanities (PW-5105612), Massachusetts Archives of the Commonwealth, Radcliffe Institute for Advanced Study at Harvard University, Center for American Political Studies at Harvard University, Institutional Development Initiative at Harvard University, and Harvard University Library. Additional archivist notes: John Appamatahqeen, John Appamatahqueen, John Appamatakqeen, innocence in murder of Thomas Eames' family at Natick, families, Goodman Eames, saved life of one Eames boy by carrying him on their backs, pardon, promise of life and liberty to enemies who submitted, Boston, Hopkinton, murder, imprisonment, jail, Moguncog Indians, Magunquog, corn, King Philip's War, Captain Tom, James Printer, Thomas Prentiss, [Thomas Prentice?], Netus, Joseph Jackstraw, William Jackstraw, Captain James Prentice, James Prentiss, [additional documents in volumes, see pages 210a-212a] Location of the petition at the Massachusetts Archives of the Commonwealth: Massachusetts Archives volume 30, pages 216-217
On October 1, 2017, the highest number of fatalities from a mass shooting in the United States was recorded when Stephen Paddock attacked a crowd of concert-goers on the Las Vegas strip, killing 58 and injuring 546 others, then taking his own life before authorities could apprehend him. Most recently, one of the worst mass shootings in the U.S. occurred in Maine on October 26, 2023, when Robert Card, an Army reservist and firearms instructor, opened fire in a bowling alley and a bar, killing 18 and injuring 13 others. Card then became the focus of a two-day-long manhunt, until he was found dead from a self-inflicted gunshot.
There were public mass shootings in the United States in every year between 1998 and 2019, resulting in a total of almost 1,900 casualties. When compared with the number of victims of mass shootings in all other developed nations (based on UN specifications), the United States' figure is often higher than all of these countries combined. There were notable exceptions, such as the attacks in Paris on the evening of November 13. 2015, which resulted in 130 deaths and 416 injuries (the same year the Charlie Hebdo shooting killed 12 people and injured 11 more), the 2011 attacks in Oslo and Utøya, Norway and Liège, Belgium which had a combined casualty count of 240 due to gunfire. In the United States, the deadliest mass shooting in this time was the Las Vegas Strip massacre in 2017.
Lynching in the United States is estimated to have claimed over 4.7 thousand lives between 1882 and 1968, and just under 3.5 thousand of these victims were black. Today, lynching is more commonly associated with racial oppression, particularly in the south, however, in early years, victims were more commonly white (specifically Mexican), and lynchings were more frequent in western territories and along the southern border. It was only after Reconstruction's end where the lynching of black people became more prevalent, and was arguably the most violent tool of oppression used by white supremacists. Nationwide, the share of the population who was black fluctuated between 10 and 13 percent in the years shown here, however the share of lynching victims who were black was almost 73 percent. North-south divide Of the 4.7 thousand victims of lynching between 1882 and 1968, over 3.5 thousand of these were killed in former-Confederate states. Of the fourteen states where the highest number of lynching victims were killed, eleven were former-Confederate states, and all saw the deaths of at least one hundred people due to lynching. Mississippi was the state where most people were lynched in these years, with an estimated 581 victims, 93 percent of whom were black. Georgia saw the second most lynchings, with 531 in total, and the share of black victims was also 93 percent. Compared to the nationwide average of 73 percent, the share of black victims in former-Confederate states was 86 percent. Texas was the only former-Confederate state where this share (71 percent) was below the national average, due to the large number of Mexicans who were lynched there. Outside of the south Of the non-Confederate state with the highest number of lynching victims, most either bordered the former-Confederate states, or were to the west. Generally speaking, the share of white victims in these states was often higher than in the south, meaning that the majority took place in the earlier years represented here; something often attributed to the lack of an established judiciary system in rural regions, and the demand for a speedy resolution. However, there are many reports of black people being lynched in the former border states in the early-20th century, as they made their way northward during the Great Migration. Between 1882 and 1968, lynchings were rare in the Northeast, although Connecticut, Massachusetts, New Hampshire and Rhode Island were the only states** without any recorded lynchings in these years.
Most estimates place the total number of deaths during the Second World War at around 70-85 million people. Approximately 17 million of these deaths (20-25 percent of the total) were due to crimes against humanity carried out by the Nazi regime in Europe. In comparison to the millions of deaths that took place through conflict, famine, or disease, these 17 million stand out due to the reasoning behind them, along with the systematic nature and scale in which they were carried out. Nazi ideology claimed that the Aryan race (a non-existent ethnic group referring to northern Europeans) was superior to all other ethnicities; this became the justification for German expansion and the extermination of others. During the war, millions of people deemed to be of lesser races were captured and used as slave laborers, with a large share dying of exhaustion, starvation, or individual execution. Murder campaigns were also used for systematic extermination; the most famous of these were the extermination camps, such as at Auschwitz, where roughly 80 percent of the 1.1 million victims were murdered in gas chambers upon arrival at the camp. German death squads in Eastern Europe carried out widespread mass shootings, and up to two million people were killed in this way. In Germany itself, many disabled, homosexual, and "undesirables" were also killed or euthanized as part of a wider eugenics program, which aimed to "purify" German society.
The Holocaust Of all races, the Nazi's viewed Jews as being the most inferior. Conspiracy theories involving Jews go back for centuries in Europe, and they have been repeatedly marginalized throughout history. German fascists used the Jews as scapegoats for the economic struggles during the interwar period. Following Hitler's ascendency to the Chancellorship in 1933, the German authorities began constructing concentration camps for political opponents and so-called undesirables, but the share of Jews being transported to these camps gradually increased in the following years, particularly after Kristallnacht (the Night of Broken Glass) in 1938. In 1939, Germany then invaded Poland, home to Europe's largest Jewish population. German authorities segregated the Jewish population into ghettos, and constructed thousands more concentration and detention camps across Eastern Europe, to which millions of Jews were transported from other territories. By the end of the war, over two thirds of Europe's Jewish population had been killed, and this share is higher still when one excludes the neutral or non-annexed territories.
Lebensraum Another key aspect of Nazi ideology was that of the Lebensraum (living space). Both the populations of the Soviet Union and United States were heavily concentrated in one side of the country, with vast territories extending to the east and west, respectively. Germany was much smaller and more densely populated, therefore Hitler aspired to extend Germany's territory to the east and create new "living space" for Germany's population and industry to grow. While Hitler may have envied the U.S. in this regard, the USSR was seen as undeserving; Slavs were the largest major group in the east and the Nazis viewed them as inferior, which was again used to justify the annexation of their land and subjugation of their people. As the Germans took Slavic lands in Poland, the USSR, and Yugoslavia, ethnic cleansings (often with the help of local conspirators) became commonplace in the annexed territories. It is also believed that the majority of Soviet prisoners of war (PoWs) died through starvation and disease, and they were not given the same treatment as PoWs on the western front. The Soviet Union lost as many as 27 million people during the war, and 10 million of these were due to Nazi genocide. It is estimated that Poland lost up to six million people, and almost all of these were through genocide.
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(:unav)...........................................
The deadliest school shooting in the United States as of September 4, 2024, was the Virginia Tech massacre, with 32 fatalities and 23 injuries. The next deadliest school shooting (based on fatalities) was the Sandy Hook Elementary massacre in Newtown, Connecticut, with 27 fatalities. School shootings in the U.S. Mass shootings in the United States have become a disturbingly common occurrence, and sadly, so have school shootings. The Columbine school shooting is perhaps the most famous in the country’s history, and since 1999 (when the shooting occurred), the number of school shootings has only increased. Many measures have been used to try to prevent school shootings, including security guards and metal detectors being deployed in schools, and even the suggestion that teachers be allowed to carry guns in schools. Gun control Gun control in the United States is a sticky issue, since gun ownership is enshrined in the Constitution. Some advocate for stricter gun control laws to try to prevent future mass shootings, while others say that this is unconstitutional. Gun ownership rates in the U.S. are high, with the share of American households owning at least one firearm remaining relatively steady since 1972.
100 of the mass shootings in the United States between 1982 and September 2024 involved weapons which were obtained legally; a clear majority. Only 16 incidents involved guns that were obtained illegally. Legally owned firearms in the U.S. Within the United States, one must be at least 18 years old in order to purchase shotguns, rifles, and ammunition, and at least 21 years old to purchase all other firearms. Some people may be restricted from owning firearms, such as individuals who have been dishonorably discharged from the military or tourists. Guns must be sold through licensed dealers, and purchasers must undergo a background check. However, the much-discussed “gun show loophole” allows people to purchase firearms from a flea market, gun show, online, or from a personal collector without a background check. The national firearm conversation The right to own a gun in the United States is protected by the 2nd Amendment of the Constitution. While changing a part of the Bill of Rights (the first 10 amendments to the Constitution) would be extremely difficult, the issue of gun rights has become a highly controversial, and highly partisan, topic in the national conversation. For example, a majority of Republicans believe that if legal gun ownership is controlled, that there will not be a difference in the number of mass shootings. In contrast, most Democrats believe the number will decrease.
THIS DATASET WAS LAST UPDATED AT 8:10 PM EASTERN ON MARCH 24
2019 had the most mass killings since at least the 1970s, according to the Associated Press/USA TODAY/Northeastern University Mass Killings Database.
In all, there were 45 mass killings, defined as when four or more people are killed excluding the perpetrator. Of those, 33 were mass shootings . This summer was especially violent, with three high-profile public mass shootings occurring in the span of just four weeks, leaving 38 killed and 66 injured.
A total of 229 people died in mass killings in 2019.
The AP's analysis found that more than 50% of the incidents were family annihilations, which is similar to prior years. Although they are far less common, the 9 public mass shootings during the year were the most deadly type of mass murder, resulting in 73 people's deaths, not including the assailants.
One-third of the offenders died at the scene of the killing or soon after, half from suicides.
The Associated Press/USA TODAY/Northeastern University Mass Killings database tracks all U.S. homicides since 2006 involving four or more people killed (not including the offender) over a short period of time (24 hours) regardless of weapon, location, victim-offender relationship or motive. The database includes information on these and other characteristics concerning the incidents, offenders, and victims.
The AP/USA TODAY/Northeastern database represents the most complete tracking of mass murders by the above definition currently available. Other efforts, such as the Gun Violence Archive or Everytown for Gun Safety may include events that do not meet our criteria, but a review of these sites and others indicates that this database contains every event that matches the definition, including some not tracked by other organizations.
This data will be updated periodically and can be used as an ongoing resource to help cover these events.
To get basic counts of incidents of mass killings and mass shootings by year nationwide, use these queries:
To get these counts just for your state:
Mass murder is defined as the intentional killing of four or more victims by any means within a 24-hour period, excluding the deaths of unborn children and the offender(s). The standard of four or more dead was initially set by the FBI.
This definition does not exclude cases based on method (e.g., shootings only), type or motivation (e.g., public only), victim-offender relationship (e.g., strangers only), or number of locations (e.g., one). The time frame of 24 hours was chosen to eliminate conflation with spree killers, who kill multiple victims in quick succession in different locations or incidents, and to satisfy the traditional requirement of occurring in a “single incident.”
Offenders who commit mass murder during a spree (before or after committing additional homicides) are included in the database, and all victims within seven days of the mass murder are included in the victim count. Negligent homicides related to driving under the influence or accidental fires are excluded due to the lack of offender intent. Only incidents occurring within the 50 states and Washington D.C. are considered.
Project researchers first identified potential incidents using the Federal Bureau of Investigation’s Supplementary Homicide Reports (SHR). Homicide incidents in the SHR were flagged as potential mass murder cases if four or more victims were reported on the same record, and the type of death was murder or non-negligent manslaughter.
Cases were subsequently verified utilizing media accounts, court documents, academic journal articles, books, and local law enforcement records obtained through Freedom of Information Act (FOIA) requests. Each data point was corroborated by multiple sources, which were compiled into a single document to assess the quality of information.
In case(s) of contradiction among sources, official law enforcement or court records were used, when available, followed by the most recent media or academic source.
Case information was subsequently compared with every other known mass murder database to ensure reliability and validity. Incidents listed in the SHR that could not be independently verified were excluded from the database.
Project researchers also conducted extensive searches for incidents not reported in the SHR during the time period, utilizing internet search engines, Lexis-Nexis, and Newspapers.com. Search terms include: [number] dead, [number] killed, [number] slain, [number] murdered, [number] homicide, mass murder, mass shooting, massacre, rampage, family killing, familicide, and arson murder. Offender, victim, and location names were also directly searched when available.
This project started at USA TODAY in 2012.
Contact AP Data Editor Justin Myers with questions, suggestions or comments about this dataset at jmyers@ap.org. The Northeastern University researcher working with AP and USA TODAY is Professor James Alan Fox, who can be reached at j.fox@northeastern.edu or 617-416-4400.