"I want to know what happened. Can you tell me?" Ask why and how it happened. Know the ins and outs of things.
Under the condition of ensuring that the facts are more accurate and objective, analyze it again: "Tell mom and dad, who do you think is right and who is wrong?" If you encounter such a situation in the future, what do you think is better? " .
You can give him some parental advice as an option, but it can't be mandatory. Try to do this first.