For children: give space when asked, do not crowd, film, tease or demand an explanation, and get an adult if someone is hurt or you are worried. You are allowed to keep your own boundaries. You are not responsible for managing another child's distress.
For parents: listen to your child's account and ask the responsible adult what happened, what protection and support were provided, and what will change. Your child does not have to tolerate harm or maintain an unwanted friendship. You can seek these answers without another child's diagnosis. See protection and separate accounts and stigma and disclosure.
For bullying or exclusion, use the instructions for this role.