An analysis of over five decades of active shooter incidents in K–12 schools found that in three in four of these incidents, the shooter or shooters were school-age and were current or former students.

New York City Police Department, “Active Shooter: Recommendations and Analysis for Risk Mitigation,” 2016, https://on.nyc.gov/2nWHM4O. The New York City Police Department defines an active shooter as “a person(s) actively engaged in killing or attempting to kill people in a confined and populated area.” Everytown limited its analysis of this data to incidents that took place in K–12 schools and defined school-age as under the age of 21.