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]