So? Then he'll bother someone tomorrow.
Seriously, this is how this stuff goes on forever. I'm not blaming you, but at the same time, when this happens to people and they keep quiet about it, it only sets things up for the perpetrator (yes, I am using criminal justice words and it's for a good reason as this is battery) to do it again and to gain more confidence that he can do whatever the hell he wants to.
I know you are scared and I respect that - so tell an adult and let them handle it. This does not have to be your responsibility to fix.