Total deaths in U.S. mass shootings from 1982 to 2021, shaded to indicate the beginning and end of the Federal Assault Weapons Ban.^[1]

 

Locations of US mass shootings in 2015, according to Shooting Tracker.

Mass shootings are incidents involving multiple victims of firearm-related violence. The precise inclusion criteria are disputed, and there is no broadly accepted definition.^[2][3][4] 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, one 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.^[5][6] Using a similar definition, The Washington Post records 163 mass shootings in the United States between 1967 and June 2019.^[7]

Gun Violence Archive, frequently cited by the press, defines a mass shooting as firearm violence resulting in at least four people being shot at roughly the same time and location, excluding the perpetrator.^[8][9] Using this definition, there have been 2,128 mass shootings since 2013, roughly one per day.^[8][10]

The United States has had more mass shootings than any other country.^{[5][11][12][13][14][15]} Shooters generally either die by suicide afterward, or are restrained or killed by law enforcement officers or armed^[16] civilians.^[17] Mass shootings accounted for under 0.2% of homicides in the U.S. between 2000 and 2016.^[18]