Appendix I: Active Shooters vs Mass Shooting vs Mass Killing

This report focuses on a particular type of firearm violence, and the data it provides might differ from those used in broader categories like mass shootings or mass killings.

The terms “mass shooting” and “mass killing” are sometimes used interchangeably, and they can overlap with what are called active shooter incidents.

While some attacks can fall into more than one of these categories, not every mass shooting or mass killing meets the criteria of an active shooter incident.

To help make these distinctions clear, the following chart differentiates the characteristics of active shooter attacks, mass shootings, and mass killings.

Note: All injuries and fatalities do not include the shooter.

Definition | One or more individuals actively engaged in killing or attempting to kill people in a populated area | Three or more individuals injured and/or killed in a single incident | Three or more individuals killed in a single incident excluding the shooter

Requires Use or Attempted Use of | Yes | Yes | No Firearm

Number of Casualties Required | None | At least three | At least three fatalities

Exclusionary Factors • | Gang violence • | Drug-related violence • | Residential or domestic disputes • | Self-defense • | Barricade/Hostage situation • | Shootings in relation to another criminal act • | Crossfire as a byproduct of another ongoing criminal act None None

46 Refers to the FBI’s definition of an active shooter.

48 The Investigative Assistance for Violent Crimes Act of 2012 and Attorney General Order 3365-2013 (02/25/2013) tasked the FBI to research active shooter incidents beginning with the year 2000.