the first place to start getting help is with a psychiatrist who can evaluate your son and make therapeutic suggestions. Ask your doctor for a referral or call the local mental health agency for a referral.
Try talking to him to see why he gets so angry sometimes. Perhaps he is having trouble with someone at school or even at home. Maybe he is doing something he shouldn't and the guilt is playing out in anger.
Of course I am not a Dr. so please seek help from them for him.
Options include your family doctor, ?school counselor, etc.
If you fear for either your or his safety then try your local hospital or police.
Your son needs to be assessed and then appropriate treatment sought.
At the very least he needs to find more adaptive ways of channeling his anger.
J