What is a mass shooting? Definitions can vary

While there is not a specific definition of a mass shooting, an accepted one says that an incident in which at least four people are shot (injured or killed) is considered a "mass shooting."

The FBI uses a similar definition for a "mass murder," only the Bureau considers an incident a mass murder if three or more people are killed.

Federal statutes define "mass killing" as three or more people killed, regardless of weapons.

Mass Shooting Tracker, a website that tracks shooting incidents across the country, defines a mass shooting as any incident in which four or more people are shot, whether injured or killed.

By anyone's definition, a mass shooting can be carried out by an individual or by a group.

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