A mass shooting is an incident involving multiple victims of gun violence. The United States' Congressional Research Service acknowledges that there is not a broadly accepted definition, and defines a "public mass shooting" as one in which four or more people selected indiscriminately, not including the perpetrator, are killed, echoing the FBI definition of the term "mass murder". Another unofficial definition of a mass shooting is an event involving the shooting (not necessarily resulting in death) of 10 or more people with no cooling-off period. Related terms include school shooting and massacre. The lack of a single definition can lead to alarmism in the news media, with some reports conflating categories of crimes.