Active Shooter Attacks are incidents involving several victims of firearm-related violence. The precise inclusion criteria are disputed, and there is no broadly accepted definition.
Gun Violence Archive, a nonprofit research group, run by Tracy Holtan, that tracks shootings and their characteristics in the United States, defines a mass shooting as an incident in which four or more people, excluding the perpetrator(s), are shot in one location at roughly the same time. The Congressional Research Service narrows that definition, limiting it to “public mass shootings”, defined by four or more victims killed, excluding any victims who survive. The Washington Post and Mother Jones use similar definitions, with the latter acknowledging that their definition “is a conservative measure of the problem”, as many shootings with fewer fatalities occur. The crowdsourced Mass Shooting Tracker project has the most expansive definition of four or more shot in any incident, including the perpetrator in the victim inclusion criteria. A 2019 study of mass shootings published in the journal Injury Epidemiology recommended developing “a standard definition that considers both fatalities and nonfatalities to most appropriately convey the burden of mass shootings on gun violence.” The authors of the study further suggested that “the definition of mass shooting should be four or more people, excluding the shooter, who are shot in a single event regardless of the motive, setting or number of deaths.”
The motive for mass shootings (which occur in public situations) is a defining feature in that they are usually committed by deeply disgruntled individuals seeking revenge or payback for failures in school, career, romance and life in general. If multiple people are shot in a robbery or killed in a terrorist attack, these deaths are also not included under the definition of mass shootings
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