Mass shooting

A mass shooting is a crime in which one or more attackers use gun(s) to kill or injure multiple individuals in rapid succession. Mass shootings with multiple deceased victims are a form of mass murder. There is no widely accepted specific definition of the term, and different organizations tracking such incidents use different criteria. Mass shootings are characterized by the targeting, often indiscriminate, of victims outside a combat setting, and the term generally excludes gang violence, shootouts, and self-defense. The perpetrator of an ongoing mass shooting may be referred to as an active shooter.

Mass shootings may be done for personal or psychological reasons, such as by individuals who are deeply disgruntled, seeking notoriety, or are intensely angry at a perceived grievance; though they have also been used as a terrorist tactic, such as when members of an ethnic or religious group are deliberately targeted. It has been theorized that media coverage of mass shootings has contributed to later shooters being motivated by fame-seeking. After mass shootings, mental health issues such as survivor's guilt and post-traumatic stress disorder are commonly suffered by survivors, first responders, and victims' loved ones.

The number of people killed in mass shootings is difficult to determine due to the lack of a commonly agreed upon definition. In the United States—the country with the most mass shootings—there were 103 deaths in mass shootings in 2021 (excluding the perpetrators) using the FBI's definition, and 706 deaths using the Gun Violence Archive's definition.