A bully wants an audience. Don’t give them yours. Walk away and tell someone you trust.

Nearly all of it is a performance, and a performance needs people watching. The target is chosen for the reaction it will produce in front of others, which means none of this was ever about you or anything you did. Taking the audience away removes the point of the whole thing, though that does not make it your job to fix alone.

If you can, leave rather than reply, and go somewhere there are people you like. Then tell an adult you trust, not because you cannot handle it, but because it should not be yours to handle by yourself.