1. A person who is actively committing illegal violence by discharging a firearm at people. The term denotes that the shooter is still on the scene, has not yet been apprehended or stopped, and has the likely potential to claim more victims.
2. [FBI definition since 2014] One or more individuals actively engaged in killing or attempting to kill people in a populated area.
The term loosely implies a mass public shooting, though since 2014 the FBI uses the terms separately for very different classifications.
The term is never used to refer to police or military action, which is presumed to be legal.
Semantics & Grammar
“Active” is not a type of shooter; it is a temporal state. After the shooting is over, the shooter is no longer an active shooter. Therefore, use of the phrase “active shooter” in the past or future tense can be problematic. Creative writers using the past tense, or authors of public service announcements using the future tense, should be mindful of the semantics. Journalists should probably drop the word “active” unless they are reporting live during a shooting situation that is actively taking place.
- “What to do in case of an active shooter,” is correct usage, given the understanding that the recommendations apply during the moments of a hypothetical shooting incident in the future. In fact, this is the purpose for which the term was coined.
- “There was an active shooter at the school yesterday,” is semantically incorrect. Yesterday, while the shooting was taking place, they were an active shooter. Today, the same person is just a shooter.
- “I was hiding under my desk because there was an active shooter,” is correct usage, given the understanding that the hiding and the shooting were taking place simultaneously.
This said, the FBI in 2014 introduced a definition and a category of statistical data for “active shooter” that ignores the semantic problems, and I guess we have to live with it.