I don't know -
DD would hit us and it's generally out of frustration or tiredness. In these situations we would use time out, just facing her against a wall away from us until she had calmed down and was ready to say she was sorry. We did nickname her John Howard for a while as she would refuse to say sorry
but she could always tell us what she had done that had made mummy upset so she knew why she was there.
Sometimes I think the frustration came from being over-stimulated so the facing the wall removed all the stimulation and calmed her down. But I don't know if this is why your
DS is doing it. If time out isn't your thing then maybe a calm down cushion that he can sit on until he settles down or something like that might be an alternative.