Aggressive 4 year old beats anyone when he is upset, What should I do?

I think you need to put him on a time-out in his room to diffuse the anger. No warnings or anything, etc. He sounds like a very troubled little boy and I think this technique will work for him. Any time he misbehaves or becomes violent with you or anyone else you need to say "We don't hit/kick/bite. You are going on time-out in your room now until you can come out and say you're sorry." This is the zero tolerance technique. Remember to follow through and put him in his room. Say "I put you in time-out because you hit/kicked/bit Mommy. Now you will stay in time-out until you are ready to tell mommy your'e sorry." SInce he is so troubled and violent, he won't be put on time-out for 4 minutes like the traditional timeout. When he is ready to say he is sorry then he can come out and appologize. If he decides to come out without appologizing, then put him back in his time-out and say "You can come out of your time-out once you appologize. Are you ready to say sorry to Mommy yet?" If he does then let him out and give him hugs and kisses, but if not make him sit in timeout until he is ready to say he is sorry. Also, you might want to make a time-out reward system since he is so violent. Every time he takes a time-out and says he is sorry, you can give him a sticker, piece of candy, cookie, etc. If you don't see improvements, you might want to ask his pediatrician what to do. Hope this helps!