Hi there and welcome to med help. You don't mention how old your boy is. That would really help. There could be different things going on. First, some kids do have emotional distress from parents splitting up. The back and forth between parents houses can be hard on kids emotionally and they show it by acting out. It's important to have consistent rules at each house and to make the transitions as seamless as possible.
Now, it could also be a lack of impulse control and inability to regulate emotion. My own son has sensory integration disorder and his preschool years were rough. He didn't hit but did other things that we had to correct. I found that he needed help to gain control of his emotions. he'd go from 0 to 10 in terms of getting angry. My role is to teach him how to not be a hot head. how to handle lifes disappointments or moments in which he is angry with appropriate reactions. I started keeping a log book of what set him off and looked for patterns. I changed what I could. But I also noticed that some things that didn't make sense were causing him distress (a hallmark of sensory). Because we can't control our world, I had to teach him how to handle himself when angry. I could tell him he couldn't do X,Y and Z but I had to replace it with things he could do. For kids with emotional outbursts, it is really helpful to have a go to 'quiet spot' or 'cool down' spot in which no one can bother him and he can go to collect himself. Enclosed areas are excellent for this (such as a pop up tent, under a table, we have a pillow pile behind a chair for this purpose). He can count to 10, he can take slow deep breaths in and out, he can open and close his fists, he can use his words to ask for help from an adult, he can use his 'helping hands' (use finger paint and have him put hand prints on paper. Hang them at his height and tell him when upset to go use his helping hands--- he then pushes against them which creates pressure and is soothing to the nervous system), he can give himself a hug, etc. When he starts to get upset, say "you look like you are upset, what can we do to feel better?" Then he has all the above options to try.
There is a great book for kids too called "Hands are not for Hitting." It is really great and sends home that message.
Add/adhd is another option to look into.
By the way, how is your son's fine motor and speech?
This sounds to me like some sort of condition, to be determined by pediatric behavioral specialists. Please look into this. - Blu