I’ll concede about the food off the floor. I didn’t even read that part. Read the first part and already knew what I thought about the situation. Everything else absolutely sounds like a personal problem and one that no boss is going to be able to solve regardless of what actions they take short of just firing both parties. He can discipline who he sees fit but the animosity and resentment will still exist and will fester to eventually come out in a potentially disastrous way. It’s better to just go outside and handle it the old fashioned way. Chances are, the aggressor will back down before it even escalates any further. Sometimes, people just need to be checked. If someone threw something at my head with the intention of harming me, I’m going to make certain that they don’t again. Even if I get the worst end of things, i bet they won’t do it again.