I'm not sure what was happened, I wasn't there, but some speculation on it...
Prior reports have always said that Rihanna is extremely controlling (to the point where if she were a guy, people would have labeled her as abusive by now) in her relationship with Chris Brown, and who knows what the hell they were arguing about. Women can get vicious too--I've had friends throw glass vases and frying pans at their boyfriends, and claw them with their nails leaving scars across their arms--whilst fighting. We only know what he did to her, and while what he did was horrible (and setting a bad example as well, mind you), we have no idea what Rihanna did to him or if he acted in self defense.
So I'm not going to hate him until the whole story is out.
Chris beat up Rihanna, nobody knows why. He hit her several times and bit her as well He turned himself into the police and Rihanna doesn't want to press any legal charges However, he may face 5-10 years in jail.
Rihanna has bruises, Chris has bruises on his knuckles from hitting her so hard
they probably got in an argument and Chris brown was tired of it and got out of lose in anger, and couldn't take it anymore! That's the likely possibility