Brown also alluded to a breakup with Rihanna by changing his relationship status to "single" from "in a relationship."
ABCNews.com's calls to Brown's representative to authenticate the reported Facebook updates were not immediately returned.
If Brown did indeed hit Rihanna early Sunday morning, it may not have been the first time. According to TMZ.com, the 20-year-old pop star told police that Brown had abused her before the weekend attack that reportedly left her bruised and bloodied, and the violence was getting progressively worse.
Us Weekly magazine also quoted unnamed sources close to Rihanna who claim this isn't the first time Brown's beaten and bruised her.
While representatives for Brown and Rihanna refuse to release details about the alleged altercation that reportedly landed her in the hospital and earned him a felony domestic abuse charge, rumors are swirling about what could have precipitated the fight.
One of the latest: Brown was flirting with British singer Leona Lewis, and Rihanna flew into a rage.
According to the British paper the Daily Mirror, Brown was speaking to Lewis at a pre-Grammy party in Los Angeles hours before the late-night attack. While the conversation was innocent, it "set Rihanna off," according to an anonymous source quoted by the paper.
Other reports claim Rihanna got upset over a text message.
"He got a booty call. He got a text," an unnamed source told the New York Daily News. "Rihanna saw it and she got upset. They started to argue. She got out of the car. He wanted her to get back in, so he grabbed her. She pulled away. That's when she's told people he hit her."
Meanwhile, despite the abuse allegations against him, Brown was up for a trophy at the NAACP's annual awards ceremony tonight, as was Rihanna.
In the end, however, neither Brown nor Rihanna attended the awards and neither won. Jamie Foxx beat Brown for outstanding male artist, an award Brown won last year, and Beyonce beat Rihanna in the outstanding female artist category.
The NAACP did not immediately reply to ABCNews.com's request for comment before the ceremony.
Advertisers and radio stations have already backed away from the R&B singer. His "Got Milk" ad campaign will end this week.
"The Milk Mustache campaign is taking the allegations against Chris Brown very seriously," the company said in a statement. "We are very proud and protective of the image of the Milk Mustache campaign and the responsible message it sends to teens. Mr. Brown's ad was launched last fall and is scheduled to end this week."
Wrigley's announced Monday it would suspend its ad campaign featuring Brown as the spokesman for Doublemint gum.
"Wrigley is concerned by the serious allegations made against Chris Brown," the company said in a statement. "We believe Mr. Brown should be afforded the same due process as any citizen. However, we have made the decision to suspend the current advertising featuring Brown and any related marketing communications until the matter is resolved."
Radio stations in Cleveland, Pittsburgh and Indianapolis have pulled Brown's music in light of the abuse allegations. Radio host Java Joel of Cleveland's 96.5 WAKS-FM said he stopped airing the songs Monday when outraged listeners called to criticize Brown, according to the station's Web site.
Though officials refuse to confirm whether Rihanna is the accuser in the domestic abuse case, members of the hip-hop world and Hollywood are rallying around her and Brown.
"I was completely devastated by the concept of what I heard," Kanye West said Tuesday on Ryan Seacrest's KIIS-FM radio show. "Rihanna is so important to our culture ... to pop music. ... Her taste level and her age. ... She has the potential to be the greatest artist of all time."
"In that sense, I feel like that's my baby sis," West said. "I would do any and everything to help her in any situation."
According to Us Weekly magazine, rap mogul Jay-Z, who discovered and mentored Rihanna, "hit the roof" when he found out about the alleged fight.
Actor Terrence Howard came to Brown's defense Tuesday, telling Hollywood.tv, "Chris is a great guy. He'll be all right. And Rihanna knows he loves her."
But Wednesday, he released a statement saying, "When they asked me about Chris Brown the other day, I was in no way aware of what he had been accused of. Had I known, I would have never had said something so insensitive."
Rapper T.I., who is set to begin a yearlong jail sentence for federal weapons charges next month, told "Last Call's" Carson Daly that he spoke with Brown Monday and that the singer's "cool."
"He cool, you know. I guess he a little concerned about the situation, but he's still the same Chris," T.I. said. "I told him this too shall pass."
Mystery Surrounds Alleged Altercation With Rihanna
Sunday was a dark day for one of America's most promising stars. Chris Brown was a triple threat. He sang hit songs ("Kiss Kiss," "Forever"), danced circles around the competition (with moves comparable to those of Usher and Michael Jackson) and made inroads into the acting world ("The O.C." and "Stomp the Yard.")
He's more of a Jonas Brother than a Lil Wayne or a young Jay-Z. He doesn't sing about a gangster past; he doesn't rock blinding quantities of bling. He shot to fame in 2005, at age 16, with "Run It!" -- the hit topped the Billboard Hot 100 and made Brown the first male artist to have his debut reach No. 1.
Now, Brown's clean-cut image may be shot. He turned himself in to Los Angeles authorities Sunday night for allegedly assaulting a woman. He was booked and released on $50,000 bail; he's scheduled to go to court next month.
"I can confirm that the LAPD was at the DA's office and presented the case," a representative from the L.A. District Attorney's office told ABCNews.com Tuesday. "[The case is] regarding Chris Brown and that's all we're saying."
While officials won't reveal the identity of the woman who they say called 911 early Sunday morning and identified Brown as her attacker, eyewitnesses saw a badly bruised Rihanna check into L.A.'s Cedars-Sinai Hospital Sunday. She and Brown were supposed to appear and perform at the Grammy Awards that night.
According to E! News, Rihanna, 20, checked out of the hospital Monday night and postponed a concert scheduled for Friday in Malaysia. She also canceled a Thursday concent in Indonesia. The L.A. Times reports she's cooperating with investigators to build a domestic violence case against Brown. Meanwhile, according to the National Basketball Association, Brown has pulled out of scheduled appearances at this weekend's NBA All-Star game.
Neither Brown nor Rihanna's representatives responded to ABCNews.com's requests for comment.
Chris Brown's Rage-Filled Past
Brown's alleged violent behavior may be rooted in his past. In 2007, he told Giant magazine about how he grew up terrified, watching his stepfather abuse his mother.
"He used to hit my mom," Brown told the magazine. "He made me terrified all the time, terrified like I had to pee on myself. I remember one night he made her nose bleed. I was crying and thinking, 'I'm just gonna go crazy on him one day.' ... I hate him to this day."
Brown also told Giant he studied martial arts to defend himself. After a fight with classmates in which he broke out his moves, he begged his own mother not to go to the police.
"Don't go to no cops pressing no charges," he told her, according to Giant. "Like, we don't do that in the 'hood."
"Chris Brown is like the all-American guy," Giant editor in chief Emil Wilbekin told ABCNews.com. "He's hardworking and a great talent. He may just be reacting based on what he knows, but it's scary and surprising."
Will Companies Flock to Chris Brown Again?
For Brown, fallout's come fast. Marvet Britto, founder of brand management firm The Britto Agency, speculated that the case against the R&B singer will doom potential product endorsements and spokesperson gigs.
"Chris Brown's pedigree is not a pedigree that is indicative of bad behavior," she said. "You wouldn't expect him to have bad behavior. His career is not built on transgressions the way someone like Lil Wayne's is. Lil Wayne has built a career on smoking weed and doing drugs; that's also the pedigree of most rap stars. Chris Brown is a teenage pop star, and with that comes a more wholesome persona. And also a larger responsibility because he's targeting and speaking to a younger audience, versus a Lil Wayne whose audience is more mature and able to differentiate fact from fiction.
"His foolish acts will greatly hamper his ability to continue to see lucrative endorsement deals and corporate sponsorships," Britto said. "This will damage him."
But, perhaps, not beyond repair. America loves a comeback. If Brown apologizes for his actions, seeks help and perhaps even uses this episode for inspiration, he could set his career back on track.
"He should be given an opportunity to redeem himself," Britto said. "He should be given the opportunity to show remorse and sincerity. And now, if indeed Rihanna is the victim, domestic abuse may have two of the biggest advocates anyone could dream to have. Maybe he needs help. Maybe this will inspire his lyrics. Maybe this will end up being a blessing."