And she detailed what happened the night of the beating. She saw a text from Brown's old girlfriend, catching him in a lie. She wouldn't let in go and he, caught, got annoyed that she wouldn't drop it. Rihanna made clear it was a verbal argument and that she never hit him. She said, in fact, she wasn't interested in hurting him. She just wanted the beating to stop.

His eyes were blank and she thought he was beating her "like he has nothing to lose." That's a pretty powerful description of blind rage.

She said that he had never hit her before, but after Diane pointed out other reports saying he did, Rihanna admitted that she meant he never beat her like THAT before. (Chris Brown denies that there were other incidents. Did he mean other 'bad' incidents? Does he really not remember? Is he really that sick?)

We're told after the interview, Brown freaked out, storming into his dressing room and screaming so loud, the people in hair and makeup became alarmed and called security.

We're told Brown was out of control, and one source present tells us he smashed a window in his dressing room, and the glass shattered and some shards fell onto 43rd and Broadway. ABC security tells TMZ ... the window was shattered with a chair.

We're told by the time security rushed the area, Brown had ripped off his shirt and left the building, blowing off another performance he was supposed to do for the ABC website.

And sources say ... on his way out of the building, Brown confronted a segment producer, got in his face and stared him down. People from the show got in between Chris and the producer to diffuse the situation.

Remember -- Brown is on probation for the felony beating and he's required to obey all laws.

UPDATE 6:49 AM PT: Brown just tweeted, "I'm so over people bringing this past s**t up!!! Yet we praise Charlie sheen and other celebs for there bulls**t."

UPDATE 6:59 AM PT: Brown has already deleted the previous tweet ... and added a new one that reads, "All my fans!!! This album is for you and only you!!! I'm so tired of everyone else!! Honestly!! I love team breezy!!"

UPDATE 7:48 AM PT: Glass workers just showed up to fix the window.