ABC7 News obtained cellphone video shortly after Friday's incident at the Valencia Gardens Apartments. Demonstrators marched from the apartments to the nearby Mission police substation.
The video was given to the Office of Citizen Complaints and that office will determine whether or not police went too far.
"It was not a pretty incident," said San Francisco Police Chief Greg Suhr.
Suhr spoke to ABC7 News about the altercation between police and some residents of the Valencia Gardens Apartments last Friday night in the Mission District. It was captured on cellphone video.
Police say D'Paris Williams, 20, was told by undercover police officers to stop after riding his bicycle on the sidewalk.
His cousin Selena Rodriguez told ABC7 News Williams never heard them. She said, "He was on his bike. He had his headphones on and hoody on, so he didn't hear them."
But Suhr told ABC7 News as Williams was being cited, he walked toward his apartment. That's when police grabbed his shoulder. Suhr says Williams then bit one of the officers.
"They're thinking, 'Does this person have a gun? Is the bicycle stolen? Is the person up to something else?'" said Suhr.
The undercover police are members of the Violence Reduction Team. That unit has confiscated 10 guns in the area in the last 30 days. But on Friday night, no guns were ever found and as the arrest was happening, a crowd gathered and tried to intervene.
Rodriguez says her brother seen on video with a bloody face was also caught in the altercation.
"They over abused their power and they hurt him. They hurt him so of course his family is going to help, that's family. That's with anybody. I'm sure if you're walking on the street and you see someone being abused by the police, you're going to help them," said Rodriguez.
"The officers are also being punched at, right? Our rule is that they can use whatever force reasonable to overcome the resistance," said Suhr.
Five officers were hurt, two were taken to the hospital. The four men arrested were also injured. For now the District Attorney George Gascon decided against formally charging them, pending a further investigation.
Gascon is waiting for the surveillance video located at the apartment complex. That may or may not show Williams biting the police officer.
"I want justice for my kids because they beat up my kids and they arrested them and threw them in jail like criminals. Neither one of my children have records," said Jenifer Eaton, a San Francisco resident who demonstrated on Tuesday.
"He's upset about what happened. I mean, to me, he was profiled. Whether police think what they did was wrong or not, it was wrong," said Yvonne Quintana, Williams' aunt.
The demonstrators are planning another gathering in the neighborhood Wednesday afternoon.
ABC7 News reporter John Alston contributed to this report.
In the YouTube video of the scene, available at http://youtu.be/8NQle7jWJjc, a plainclothes officer wearing a brown shirt is seen charging at a witness.