9:54 PT -- Sources connected with Chris Brown tell TMZ ... the alleged victim is full of BS -- he was not trying to have a picture taken with Chris ... he was trying to get on Chris' tour bus, and Brown was simply trying to stop a trespass. The sources say 2 girls tried to get on the bus to have their picture taken with Chris but they were blocked, and that's when the two men -- including the alleged victim -- tried getting on.

9:42 PT --  Chris will stay in jail today and tonight.  Under DC law he can't get bail so he will have to appear before a magistrate tomorrow ... and he'll probably be released then.

9:05 PT --Victim discdlosels  Chris broke his nose and he may need surgery as early as tomorrow morning. The victim confirmed he and a friend photo bombed the two women who were taking a picture with Brown when Chris went nuts. The victim says he's not a Chris Brown fan ... and was just hanging with a couple girls at the hotel when he saw the singer outside. The victim says he doesn't understand why Brown would be "so homophobic" to hurl such a slur. And get this ... the victim says he would have accepted an apology at the scene, but now he will absolutely press charges -- and he already has a lawyer.

8:25 PT -- Law enforcement sources tell TMZ how the fight was triggered.  Two woman approached Brown in front of the W Hotel and asked to take a picture with him.  As the pic was about to be taken, 2 men rushed over to get in the photo.  We're told Chris then said, "I'm not into this gay s**t, I'm into boxing," and threw a punch at the alleged victim.  The fight was then taken to the ground.

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Chris Brown was arrested in Washington D.C. this morning for FELONY assault after allegedly attacking a man outside a hotel ... TMZ has learned.

Law enforcement sources tell TMZ ... Brown got into an argument with a man outside the W Hotel on  K Street and allegedly punched him once IN THE FACE.   We're told the man Chris struck never threw a punch.  Sources say Chris and the alleged victim did NOT know each other.

The incident occurred at about 4:30 AM.

Chris was with his bodyguard, and we're told he was also arrested.

Our law enforcement sources say Brown did not appear to be under the influence of anything at the time of the incident.

Brown is currently in custody.  As for the other person, we're told he's being evaluated at a D.C. hospital.  Sources say he's claiming injury.

Brown is still on probation in the Rihanna beating case and this could be grounds for violating his probation -- which means he could be sentenced to prison for nearly 4 years ... worst case scenario for him.

Before the incident, Chris had been hosting a party (pic below) at the nearby Park and 14th nightclub. Source: TMZ

To be updated..