You're dating a crazy bitch who goes off in a drunken rage at 4am? Instead of getting into a yelling/shoving confrontation with her he should've locked himself in a room and called the police.
Is that being realistic? I try putting myself in the same situation, had a few beers, girl going off on me slapping and scratching, I'd probably try to hold her from being able to hit me till she calmed down. Now if she continued to struggle, you could very easily see accidental bruises on her arms, but that would only be from trying to keep her from injuring me. But I can't see him running from the room, apparently with his buddies around, and hiding there till the police arrive.
I've seen it happen with a buddy and his wife. They were screaming at each other in the yard, (obviously not sterling behavior) neighbors called the cops, and he spent the night in jail. This is the best possible scenario, of course it gets worse from there. I'm just pointing out, it might not be as bad as others are saying. I hope for his sake that's all it was.