This type of aggressive behavior is not typical for a child in his age group. Intervention techniques must be utilized before he continues hurting his brother and even himself. I would suggest that you discuss this matter first with his primary pediatrician. He/she could tell you the best route to take. There are child psychologists that could help you and your son with behavior modification intervention strategies. Please seek the help that is out there.Giving him more attention at this stage is pointless. It just draws attention to the negative behavior. Just make sure that he is not a danger to himself and try to prevent violent outbursts from escalating further until professional help can be obtained.