Why Rihanna and Chris Brown broke up?

Chris Brown broke up with Rihanna or the other way round because before the grammys on ,February 8th 2009, about 12;30 in the morning Rihanna and Chris were driving then the got in a argument.

Chris stopped the car and they both got out ,when they did the argument escaladed,this left visible injuries on Rihanna.

Later police got a 911 phone call from a women[Rihanna] and said that she identified her attacker as Chris brown.

Chris was arrested later on in the day and has been released on a $50000 bail, he will be in court on March 5th.

This is why Chris and Rihanna were not at the grammys
They broke up because Chris Brown assaulted her.