"Active killer" or "active shooter" names the perpetrator of a type of mass murder marked by rapidity, scale, randomness and suicide.
SURVIVING AN ACTIVE SHOOTER - LA County Sheriff by LA County Sheriff's Dept.
The United States Department of Homeland Security defines the active shooter as "an individual actively engaged in killing or attempting to kill people in a conﬁned and populated area; in most cases, active shooters use firearms [sic] and there is no pattern or method to their selection of victims."
The United States Department of Homeland Security is a cabinet department of the United States federal government with responsibilities in public security, roughly comparable to the interior or home ministries of other countries.
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Most incidents occur at locations in which the killers find little impediment in pressing their attack.
Locations are generally described as soft targets, that is, they carry limited security measures to protect members of the public.
In most instances, shooters commit suicide, are shot by police, or surrender when confrontation with responding law enforcement becomes unavoidable.
According to New York City Police Department statistics, 46 percent of active shooter incidents are ended by the application of force by police or security, 40 percent end in the shooter's suicide, 14 percent of the time the shooter surrenders and, in less than 1 percent of cases, the violence ends with the attacker fleeing, although it must be noted that the report provides no formal definition of the relevant terms and, as a result, the scope of its statistical findings is somewhat ungrounded.
The New York City Police Department, officially the City of New York Police Department, is the largest municipal police force in the United States.