Mass murder

Mass murder is the violent crime of killing a certain amount of people, usually at least 3 or 4, and typically simultaneously or over a relatively short period of time and in close geographic proximity. A mass murder typically occurs in a single location where one or more people kill several others. Data suggests that approximately 30% of United States mass murderers die in the act. In the United States, Congress defined mass murders as the killing of three or more people during an event with no "cooling-off period" between the homicides, while in the United Kingdom the definition is four or more people killed in one act. The Investigative Assistance for Violent Crimes Act of 2012, passed in the aftermath of the Sandy Hook Elementary School shooting, clarified the statutory authority for federal law enforcement agencies, including those in the Departments of Justice and Homeland Security, to assist state law enforcement agencies, and mandated across federal agencies a definition of "mass killing" as three or more killings during an incident. A mass murder may be further classified as a mass shooting or a mass stabbing. Mass murderers differ from spree killers, who kill at two or more locations with almost no time break between murders and are not defined by the number of victims, and serial killers, who kill people over long periods of time.