From Rihanna's statement to police, as posted on Tmz.com:
"...she claims Brown "looked at [Rihanna] and said, "You just did the stupidest thing ever! Now I'm really going to kill you!"
Rihanna told cops that Brown unleashed a second wave of punches, "during which time [Rihanna] interlocked her fingers behind her head and brought her elbows forward to protect her face." He continued to punch her on her left arm, which caused a contusion on her left tricep.
At that point Rihanna tried texting her assistant. Brown threw the phone out of the car, stopped the vehicle and Rihanna then tried opening her door to get out, but Brown sped off and the door shut with Rihanna inside.
Brown placed Rihanna in a headlock while he drove, then bit her on her left ear. The car eventually stopped and Rihanna took the keys out of the ignition, and Brown began to punch her again in the face and arms. He placed her in a headlock and started applying pressure to her carotid artery. She couldn't breathe and began to lose consciousness. She tried freeing herself, and Brown bit her left ring and middle fingers and then released her."
More here.
i forgot how bad the beating was