For most children. That seemed to be an unusually violent act for a 9 year old.

In this case, remorse or no remorse, You may need to look into this further. This different than a prank or pushing or yelling. What might have happened if he had a bat at the time? I would want to get to the bottom of this and provide professional help where needed.

The potential concussion is bad, but I worry more about your son, and what’s going on with him.

Being a parent has some unforeseeable challenges. Good luck.