Speak openly with the caregiver, describe your child’s shift in behavior. Some children will embody the violence, and some will withdraw, intimidated. You, if you are paying attention you will clearly see the personality change in your child.

To act swiftly you can already know the friends your child interacts with. You will have had many conversations already and be familiar with the names of the children he shares his day with, and you will likely have met and know them all, and their parents. If he is intimidated, he may withhold the name of the bully, for fear the situation will escalate and he feels powerless. This is where a close relationship with his caregiver is of the utmost importance.

Have a conversation, describing how your child is acting out and ask whether the caregiver has noticed the same shift in behavior. The caregiver has a responsibility to address the abuse with the parent of the violator. There should be no need for you to personally address the parent, unless the caregiver is ineffectual.

Discussing parenting with other parents is a very sensitive subject matter. We take tremendous pride in how we raise our children and do not welcome criticism or even outside advice, which is an archaic egoic strategy to protect our clan. Trust in the caregiver to resolve the issue, and be patient.
Have a quiet conversation with your child, express your concern and assure him that you see that something is not right, and that you are going to protect him and resolve the issue, no matter what. “My Love, you seem so quiet, and maybe a little sad. Why are you so quiet and sad?” Or, “My Love, you used your body to hurt me. Did somebody hurt you like that? When you punch me with your fist, I feel hurt and sad. Do you feel hurt and sad when someone punches you with their fist?”

Listen to their response – even if it is without words. It may take a while for him to express himself, but you are opening up the conversation in a natural, stress free, loving way, so he feels safe.

If you are the parent of the child who is bullying, then you have to look closely at the family dynamic in your home and seek guidance from a competent professional who can help you recreate a safe, peaceful environment. You simply must prioritize the wellbeing of your child, and, of course, yourself. There are plenty of on-line resources to guide you back to sanity.

Apologize to the parents of the victim, and do so in front of your own child, who is suffering just as much. You might say, “I am so sorry that … hurt you. He has been hurt himself and we are working hard to fix the hurt and the problem, aren’t we?” Encourage your child to participate emotionally. “He won’t hurt you anymore because it is wrong and now he knows it is wrong. Let us all work on a happy friendship…”

At this age, your child is too young to be forced to apologize. He likely doesn’t yet have any concept of articulating his remorse. To forcefully coerce an apology is additional abuse!
You be the example of what mature reconciliation looks like. You be the change.