It is just a stage and he will grow out of it. I know it is quite antisocial but you just have to tell the child that no we don't hit people as it hurts and it is not nice. He will soon get the idea.

My daughter is 2 and she will scratch and scream if another child get too close or takes a toy away. If we are out and doing something like a kindergym class I just make sure I stay by her and avoid a situation where she scratches another child usually by diversion or removing her quickly from the situation. She is very slowly getting better as her language is improving. I think a lot of this behaviour stems from language frustration.