Impulse control is not an easy thing to teach. If he were a bit older there are things like when they go to do something they need to stop and count to three before doing it - most often they will not end up doing what they were going to do.

If parents are overmonopolizing his free time at home then that is part of the problem too. He doesn't know how to play by himself let alone anyone with anyone else. Sharing is not something he has to do since he is the centre of attention at home - boy is he is for a rude awakening on the realities of life.