Mass shootings in the United States

Mass shootings are incidents involving multiple victims of firearm related violence. Definitions vary, with no single, broadly accepted definition. One definition is an act of public firearm violence—excluding gang killings, domestic violence, or terrorist acts sponsored by an organization—in which a shooter kills at least four victims. Using this definition, a 2016 study found that nearly one-third of the world's public mass shootings between 1966 and 2012 (90 of 292 incidents) occurred in the United States. In 2017, The New York Times recorded the same total of mass shootings for that span of years. Perpetrator demographics vary by type of mass shooting, though in almost all cases they are male. Contributing factors may include easy access to guns, perpetrator suicidality and life history factors, and sociocultural factors including media reporting of mass shootings and declining social capital. However, reliable statistical generalizations about mass shootings are difficult to establish due to the absence of a universal definition for mass shootings, sources for data on mass shootings being incomplete and likely including biased samples of incidents, and mass shootings having low base rates. The Federal Bureau of Investigation designated 61 of all events in 2021 as active shooter incidents. The United States has had more mass shootings than any other country. After a shooting, perpetrators generally either commit suicide or are restrained or killed by law enforcement officers. Mass shootings accounted for under 0 % of gun deaths in the United States between 2000 and 2016, and less than 0 % of all homicides in the United States from 1976 to 2018.