Your letter sounds as if this behavior occurred at school. Make sure that your son's teacher is aware of the problem so that your son can be closely supervised. If it is happening in the neighborhood, another logical consequence is that he can't play with other children without an adult around at all times.
Talk with the school counselor about your son's behavior. She may be able to give him some individual time. If these behaviors continue and you decide that your son needs additional help outside the school, the counselor or your pediatrician can refer you to a therapist in your community.