When the city's 6pm curfew passed, police warned the protesters to go home or risk being arrested. An hour after that, they moved in.
The Daily News says "roughly 200 people" fled into the surrounding streets, and the police followed them.
During that mayhem, the officers fired nonlethal rubber bullets at dozens of the protesters as they entered an apartment building, seeking refuge.
One of those rounds struck the homeless man, causing a bloody injury above his left eye. Paramedics arrived shortly afterwards to treat him.
The Los Angeles Police Department (LAPD) has so far declined to comment.
"We cannot speculate on what caused this individual's injury without further investigation," it said, according to CBS radio host David Benaud.
The department yesterday said it would "thoroughly investigate" any allegations of misconduct by its officers.
"We are aware of individuals who have posted videos online and on social media depicting encounters with the police, that they believe constitutes excessive force or misconduct during these demonstrations. We will investigate each instance thoroughly, and hold any officer who violates department policy accountable," it said.
The statement listed a phone number members of the public could call to make a complaint if they believed they had been "unjustly injured".
A witness to the shooting, photographer Kirk Tsonos, posted his account of it on Facebook overnight, saying the police officers' conduct was "completely unacceptable".
"As I was being arrested for my second day in a row during peaceful protests in support of Black Lives Matter, I decided to continue taking photos until the moment right before handcuffs were put on me. Very risky, but a necessary move to expose LAPD's entirely inexcusable use of aggressive force, especially in the moments before mass arrests of peaceful protesters," Tsonos said.
"As we were being boxed in on Broadway and 5th Street to be arrested, LAPD decided that a completely unarmed homeless man in a wheelchair that had NOTHING to do with our protest was somehow a threat.
"They proceeded to inappropriately shoot 'nonlethal' rounds directly at his face, which is against the proper procedure for firing rubber bullets.
"The last image is exceptionally heartbreaking for me as you can see the homeless man writhing in pain, screaming, as he spews blood from his face moments after getting shot.
"When people want to be apathetic or inactive in fighting against police brutality against black individuals, make them realise this trickles over and can affect them or someone they love too, regardless if they're black or not.
"This is completely unacceptable. This injustice needs to be held accountable."
The past week has been littered with accusations of police going overboard in their response to the protests across the US.
Yesterday two officers from Buffalo in New York were suspended after being caught on video pushing a 75-year-old protester, Martin Gugino, to the ground. They then stood by and did nothing as he bled onto the pavement from a head injury.
Gugino is expected to recover.
"I was deeply disturbed by the video," said Buffalo Mayor Byron Brown.
"After days of peaceful protests and several meetings between myself, political leadership and members of the community, tonight's event is disheartening."
Today the city's entire 57-member emergency response team, which is deployed to deal with mass protests or riots, resigned in solidarity with the two suspended officers.
The 57 officers are still employed by the police department, but have specifically quit the emergency response team.
"Fifty-seven resigned in disgust because of the treatment of two of their members, who were simply executing orders," said John Evans, president of the Buffalo Police Benevolent Association.
In Erie, Pennsylvania, a 21-year-old woman has filed a complaint after being sprayed with mace and then kicked in the face by police.
Hannah Silbaugh was sitting in the middle of a street with her hands in the air when the officers approached her.
"When I wouldn't move, the cops kicked me," she told local reporters.
The police department is investigating, and the officer in question has been assigned to desk duty. His identity has not been revealed.
An Australian news crew was also the victim of heavy-handed police. Footage of Channel 7 reporter Amelia Brace and her cameraman being shoved and hit by cops near the White House in Washington D.C. went viral around the world.
Police said the pair "were not readily distinguishable from violent protesters", even though they were broadcasting live at the time.
