I would suggest Occupational Therapy if he doesn't already attend. If he does, talk this over with them. In the meantime, what Sarah said above is very practical. I have an 8 year old who has been aggressive since he was about 4. We do a lot of sensory exercises. Functional communication training or picture schedules are also worth looking into.

You have to in some way make him understand he cannot do this and this is not acceptable . I would try ABA if you are not doing this already and you may have to consider meds if the aggression does not stop. If you believe it is a communication issue then you have to work on that as well with speech therapy

I understand what you are dealing with because my daughter used to do the same thing but she is non verbal. Since she has been getting ABA and they have been teacher her PECS and sign language as well as being on meds she is much better. A god therapist can also teach the child to bang themselves on pillows or cushions so they do not hurt themselves. My daughter does this as well.

Other than that sometimes walking away needs to be done as well, and if you have stopped them from hurting themselves then you can do it. If the child knows they can get away with hurting you then they are going to keep on doing it

Hi, my son is also 3 and has been having trouble with aggressive behavior this past week. He's high functioning and very verbal but when he's angry he seems to prefer lashing out and screaming. I have found that ignoring him seems to cut the meltdown short but he doesn't hurt himself like your little one. My husband pointed out that he doesn't behave like that with others, just me, so maybe my reaction was feeding the behavior. Once I stopped giving him attention he calmed down. I guess I just wanted to let you know that you're not alone in this, and it is hurtful when your child is acting out.