Hedgerow
HACK
Not necessarily, but it could be. Any active threat is a terrorist of some sort IMO.
Absofreakinglutely
This^^^^, an "active threat" means somebody, (whether it be a "terrorist" as we know it, a disgruntled employee, or some misguided teenager, etc.), who is active (meaning in the process) of inflicting mass murder in your facility, institution, or building. Think Columbine, Virginia Tech, Ft. Hood, and yes, the recent ISIS/terrorist attacks; unfortunately there are many more examples. There is no warning; you are basically a potential victim in the vicinity when it goes down. Help is not expected to arrive for 5-10 minutes or maybe longer, which can be an eternity in this situation.
I.E.
Never comply..
Always fight... By whatever means necessary.