The first thing to do is to take keep a detailed diary of EVERYTHING that is said to you as well as his (or her) actions. Also make note of the time, and if anyone else was present when these confrontations occurred. At this point, you can write down what has happened in the past, and start keep an account of what's happening now on a daily basis. It doesn't have to be a long chapter about your entire day, just a few words to describe the day's events, and what interaction you had with your boss.

Next take a stroll down to HR. Tell the HR person your boss has created a "hostile work environment". Trust me, this will get their attention very quickly, especially once you let them know you been documenting what he's been doing.

If you want to get a greater reaction, mention to them you've been talking to a lawyer, and are looking at the possibility of a lawsuit against your boss, and the company for letting him get by with the way he treats you, and his staff.

That should start to get the result of backing your boss off. And, if it doesn't, talk to a lawyer. The first consultation is free, and you might find you do have the basis for a lawsuit. If you do, go for it.

Good luck.