I'm late on this but I want to answer as I'm a male in my thirties and I live in the U.S.

Every guy my age knows that they cannot, under any circumstances, get sexually involved with a minor. I don't care if you're drunk and she's doing a strip tease, you CANNOT TOUCH HER! End of story. This guy knew it because we all know it and since he went ahead anyway, he's a serious risk of offending again (except next time may be worse).

This was sexual abuse of a minor by an adult both legally and conceptually.

What to do next is up to your friend but I would strongly recommend getting away from this guy, pressing charges (if for no other reason than to get this incident on record), and getting some therapy to help deal with lingering feelings from the incident.

Cyran0