Database of mass killings and shootings in the US
A look at mass killings in the U.S.
The pattern of mass killings is random and unpredictable, but there are some common elements — as this database shows. It is a collaboration between The Associated Press and USA Today in partnership with Northeastern University, and it tracks mass killings in the United States going back to 2006.
The mass killings in so far have taken place in:
How mass killings are defined
The database defines a mass killing as an attack in which four or more people have died, not including the perpetrator, within a 24-hour period. This definition is consistent with how the FBI defines mass killings.
Where have mass killings occurred?
15
30
45
60
None
Other takeaways
The rate of mass killings has remained relatively flat, given the rise in population over time. The pattern is random and unpredictable, but there are some common elements:
Most mass killings in the U.S. involve firearms.
Of 561 total mass killings in the database, 444 (79%) involved firearms. Shooting victims make up 81% of the 2,914 victims of mass killings since 2006.
Most mass killings occur in residences, not public places.
While national media coverage tends to focus on public mass killings and indiscriminate violence, data shows a majority (around 67%) occur in and around people’s homes.
Many perpetrators of mass killings know their victims.
Mass killings involving family members made up 48% of all mass killings since 2006.
The median age of a mass killing offender since 2006 is 30. Most perpetrators of mass killings are men; victims are more evenly divided by gender.
Offenders are often killed or die by suicide at the scene.
In almost one-third of mass killings offenders died by suicide, and 6% of offenders were killed at the scene.
Explore the data
Frequently asked questions
What is the difference between a mass killing and a mass shooting?
There are variations in how mass killings are recorded and defined, and mass killings are sometimes conflated with mass shootings. There is overlap between the two categories, but using the terms interchangeably can cause confusion about the pace and frequency of occurrences.
The Gun Violence Archive uses a more inclusive definition that includes non-fatal shootings. In 2022, the Gun Violence Archive recorded 647 mass shootings, while the AP/USA Today/Northeastern database recorded 42 mass killings, 36 of which involved firearms.
How common are mass killings in schools or places of worship?
Mass killings in schools and places of worship are uncommon. There have been 13 mass killings in schools and seven in houses of worship since 2006. While rare, these mass killings resulted in some of the highest numbers of deaths.
Methodology
The AP/USA Today/Northeastern University mass killings database tracks all homicides in the U.S. since 2006 in which four or more people were killed intentionally within a 24-hour period, not including any offender and not including any fetus or embryo carried by a pregnant victim.
Researchers at Northeastern University's School of Criminology and Criminal Justice identify and classify potential mass killings using the following sources, among others:
- Supplementary Homicide Reports from the FBI
- Media accounts, both contemporaneously and in commercial archives
- Records from courts and from local law enforcement agencies
This database's definition is meant to be distinct from killing sprees, in which someone kills multiple victims in quick succession in different locations. If a mass killing occurs as part of a spree, though, we do treat it as such, and we count all victims who died within seven days of that mass killing.
This database does not include mass killings that occur outside the 50 U.S. states and Washington, D.C. Any questions or corrections concerning the data should be directed to James Alan Fox at j.fox@northeastern.edu.
CREDITS
Design and development: Koko Nakajima, Phil Holm
Graphics: Koko Nakajima, Kevin Vineys
Data analysis: Koko Nakajima, Larry Fenn
Text editing: Scott Stroud