Part I: Introduction
Active shooter attacks are dynamic incidents that vary greatly from one attack to another.
The Department of Homeland Security (DHS) defines an active shooter as “an individual
actively engaged in killing or attempting to kill people in a confined and populated area.”
In its definition, DHS notes that, “in most cases, active shooters use firearm(s) and there
is no pattern or method to their selection of victims.” The New York City Police
Department (NYPD) has limited this definition to include only those cases that spill
beyond an intended victim to others.1
The type of police response to an active shooter attack depends on the unique
circumstances of the incident. In the event of such an attack, private security personnel
should follow the instructions of the first-responders from the NYPD.
Because active shooter attacks are dynamic events, the NYPD cannot put forward a
single set of best-practices for private security response to such incidents. However, the
NYPD has compiled a list of recommendations for building security personnel to mitigate
the risks from active shooter attacks. The recommendations draw on previous studies of
active shooter attacks and are presented in Part II.2
The NYPD developed these recommendations based on a close analysis of active shooter
incidents from 1966 to 2012. This Compendium of cases, presented in the Appendix,
includes 324 active shooter incidents. It is organized chronologically by type of facility
targeted, including office buildings, open commercial areas, factories and warehouses,
schools, and other settings.
The NYPD performed a statistical analysis on a subset of these cases to identify common
characteristics among active shooter attacks. This analysis is presented in Part III and the
underlying methodology is presented in Part IV. The analysis found a large degree of
variation among attacks across some broad categories, including: sex of the attacker, age
of the attacker, number of attackers, planning tactics, targets, number of casualties,
location of the attack, weapons used, and attack resolution. The analysis also provides
insight into the frequency of active shooter attacks.