Sorry that happened to your son. I think there is only one solution. Your kids cannot play with him anymore. My son really liked the little boy across the street. He would ask to go play with him everytime he saw him outside his house (which was a lot). But the boy liked to play with sticks. And one day, I saw him hitting my son with the stick. I went right over and yelled at him. The Mom came out and criticized me for yelling at her kid. Son never played with her kid again. Not worth taking a chance.
