Instructions: Filter the data by clicking on boxes and check marks. Add or remove boxes to see where shooters fit in each criterion. Hover the cursor over the categories to see a description of some of the less common terms.
Current or former workplaces of perpetrators were the most common sites for mass shootings. Most of the shooters had been fired.
Almost all of mass shooters at restaurants, bars and retail establishments were strangers to those businesses, while perpetrators in workplaces, houses of worship, and schools and colleges tended to be current or former students and insiders known to the victims.
Of the 172 mass shooters studied, only four were women. In two cases, the women acted in partnership with a man.
While the difference in numbers between female and male mass shooters is stark, it was represented in all U.S. homicides in which 80% to 90% of offenders in a given year were men.
The most common weapon used to commit mass shootings is a handgun. Eighty percent of all mass shooters used at least one handgun during their crime. A semiautomatic assault weapon is the next most used weapon with 28% of shooters using them. Seventy-three percent of shooters who used a semiautomatic assault weapon also used a handgun at the scene.
Almost half of all mass shooters acquired all of their known guns legally through a licensed dealer, unregulated private sale or other legal means. Twelve percent of shooters stole or borrowed at least one of their guns. A third of all guns used in mass shootings have unknown origins.
More than 60% of shooters knew at least some of their victims, while 34% did not know any of their victims.
Most of the mass shooters at restaurants, bars and retail establishments were strangers to their victims, while perpetrators in workplaces, houses of worship, and schools and colleges tended to be current or former students and insiders known to the victims.
The most common background trait of mass shooters is a criminal record, at 65%, closely followed by a history of violence at 63%. Other common traits are employment troubles (51%), a history of trauma (42%), and domestic abuse (36%).
Nearly a third of all mass shooters have a high school education or lower, 27% have some experience at college or a trade school, 7% have a college Bachelor’s degree, and 6% have a graduate school degree. The education status for 28% of shooters is not known.
More than two-thirds of mass shooters had a history of mental health concerns, which is higher than the 50% of people in the general population who will satisfy criteria for a mental illness at some point in their lives.
Before they carried out their crimes, more than 80% of mass shooters displayed signs crises, described by The Violence Project as a marked change in behavior that is noticeable to others. Such behavior includes exaggerated emotional responses, an increased interest in violence and signs of hopelessness.
The Violence Project tracked many underlying reasons that helped to motivate a shooter to carry out a mass shooting. The most common motivation at 30% is psychosis, a mental condition that makes it difficult for a person to recognize what is real and what isn’t. That is followed by followed by employment troubles (23%) and interpersonal conflict (20%), defined as a non-domestic conflict with coworkers, friends or family.
Jillian Peterson, Ph.D., and James Densley, Ph.D., built a new database of mass shooters that they hope will inform future research and policy decisions about how to effectively prevent and respond to mass shootings.
For their study, they used the Congressional Research Service’s definition of a mass shooting:
“a multiple homicide incident in which four or more victims are murdered with firearms — not including the offender(s) — within one event, and at least some of the murders occurred in a public location or locations in close geographical proximity (e.g., a workplace, school, restaurant, or other public settings), and the murders are not attributable to any other underlying criminal activity or commonplace circumstance (armed robbery, criminal competition, insurance fraud, argument, or romantic triangle).”
The team collected more than 100 pieces of information on each of 172 mass shooters, resulting in The Violence Project Database of Mass Shootings in the United States, 1966 - February 2020.