With your background, you know full well there is waaaay more to this story than we'll ever know, and I'd be willing to bet money that there was more,overt aggression and probably a history. 

People shouldn't have to work in a hostile environment. If it's true that all he was doing was as staring off into space, I suspect this was overkill, but I am sure there is context we aren't privy to and Mom is either oblivious yo or doesn't work any to acknowledge.