I taught in a "common area" class which had offices stemming from it. It was an ESoL (English Speakers of Other Languages) class. It involved a lot of participation, discussion, scripts, and repeating after the teacher. I would bring my guitar and we would practice singing songs they chose.
There was a teacher who taught a small computer class in the opposite corner of the area. He was in a computer lab which was separate/in its own room. He repeatedly asked our class to be quiet, which I tried my best, but his class had headphone access and it seemed more so that we were annoying him than his students. I tried to be cordial. He verbally attacked me in front of my class and barked that we be more quiet.
I approached him privately and said if we're doing something specific, please approach me after or before class about it. I said that I wouldn't do the same thing to him while he was teaching/moderating computer access. I informed my boss after the 2nd or 3rd incident.
He was let go from the job after exploding in a public email to every worker. He insulted the boss and used pretty foul language.
After he was fired, he threatened to come to the school and harm his superiors/coworkers. We were on lockdown/heightened security for about a week following it. I believe he had some sort of issues and I hope he's gotten better, but he never did follow through with that threat and we continued to sing our songs as a class.