DHS video on dealing with active shooters
Its style is that of the 1950s, and it gives priority to running away, but at least it acknowledges that you might be forced to fight. Although I'd favor a pistol over trying to conk someone with a folding chair or a fire extinguisher.
While working for the Feds, I was actually in a situation where we tended to get telephonic threats. The security guards for the building were unarmed. I and another attorney were not. Of course this was in the days before every government building, including the officers of the dog catcher and sewer inspector, had metal detectors.