Children often react with frustration if they feel they are not communicating, or not being paid attention. You need to nip this in the bud before it gets worse. If your child hits you, hold both his hands, bend down to his level, and tell him 'No' in a firm voice without shouting. When he is calm, explain that hitting hurts Mummy and Daddy and makes them sad. Re-enforce the message as often as needed, and hopefully he will begin to calm down. balance this with lavish praise if he is calm when he would usually be violent - he'll soon appreciate that being nice is better in the long run.