When I lived in Florida, we had a guy who, upon learning he was fired, loudly threatened to come back to the office with one of his AK-47s and mow everyone down. He shouted this across to everyone in the single-floor open office as he was being physically removed from the building. And we knew he had multiple guns because we did a few company outings at a shooting range.

You better believe he was locked out as soon as he could be removed from the building, and we had armed security there for some time after his termination.