Definition of an active shooter: "an individual actively engaged in killing or attempting to kill people in a confined and populated area; in most cases, active shooters use firearms(s) [sic] and there is no pattern or method to their selection of victims."
Semantics wasn't the point. When police get reports of an active shooter on campus, you don't want to be the one seen holding a gun when they arrive.
A person who attempts to shoot an active shooter therefore satisfies the definition of an active shooter.