At 14 I would assume if hes not using drugs or having severe hormonal issues that this is not new behavior. Has he always acted out violently? What precludes this behavior?
It may be a good idea to contact the school and ask for a counsellor, he must have to go to school so thats the place to start.Why do you think he hits his Dad is there any reason?
You need help - far more than anyone on this board is able to give. Is there anyone at school who could advise you? Or your local medical doctor? Is your son into alcohol and/or drugs? Or some service club which works with "difficult" children? Sorry - but that is the best that I can do ....