"The suspect continued to advance, swinging the chain at the officer," said Oakland Police Chief Sean Whent at a news conference. "The officer drew her firearm and fired at the suspect, striking him."
A witness shared cellphone video with ABC7 News, which caught the chaotic minutes after the incident.
VIDEO: Cellphone video moments after Oakland officer-involved shooting
In the video the man, who was still alive after being shot, can be seen moving his head and arms at times on the ground while a bystander is heard calling for help, "He's dying... Someone help him!"
The officer, identified as an 18-year-veteran of the force, is visibly shaken and bloodied. In the video you see her keeping her gun trained on the man while she radios for help.
Oakland resident Michelle Harris told ABC7 News, "I ran out and then I see this man lying on the ground and I see the officer sitting on the side."
Harris says she heard the shots and recorded video on her cellphone that shows the suspect on the ground.
"She looked like she had blood on the side of her face," said Harris. "It looked like something did happen, but it was just too extreme."
Neighbors tell ABC7 News the man was a regular in the neighborhood, often sleeping wherever he could. They note that sometimes he would be combative with those who tried to get him to move along.
Police say the officer went to a residential complex at the corner of MacArthur Boulevard and Van Buren Avenue to follow-up with the victim of an assault that was reported at about 6:45 a.m.
The victim told several officers who responded to the scene at about 7 a.m. that the suspect had been trespassing in the complex's garage. According to Whent, the suspect assaulted her when she asked him to leave. The victim sustained minor injuries, but didn't have to be hospitalized. Police say the suspect didn't use the metal chain in that incident.
Whent says the responding officers, who were working the overnight shift, took some initial information from the victim but couldn't find the suspect, so they left the area.
The female officer, who was beginning her day shift, did a follow-up interview with the victim. As she got into her patrol car to drive away the suspect, who she recognized from the victim's description, walked in front of her car. Whent says the officer got out of her car but "was immediately attacked by the suspect with a metal chain."
The officer suffered injuries to her head and face, but she is expected to be okay. She's been placed on paid administrative leave.
Some in the community are questioning the use of force in this incident.
"Instead of shooting him, they could've tasered him or maced him," Oakland resident Rebecca Ellis said. "I don't think what he did was worth his life being taken, just by knowing him personally."
Fellow Oakland resident Carrie Mason added, "It is kind of a disgrace that you have to shoot someone eight times over swinging a bicycle chain, or whatever the situation may be, it was not a cause to die."
Harris, who took the cellphone videos, agrees, "I think she should have used her skills a little bit more better (sic) to avoid the contact of the bike chain, where she wouldn't have to go so far to using her gun,."
Demonstrators from the Coalition to Defend Affirmative Action By Any Means Necessary held a demonstration and rally Thursday night to protest the shooting.
This was the sixth officer-involved shooting in Oakland and the fourth fatal one this year. On June 6, Demouria Hogg was shot and killed four blocks east of Thursday morning's shooting after police say he reached for a loaded handgun. On Aug. 3, Oakland officers shot and killed 49-year-old Antonio Clements after he allegedly wounded a sergeant with an AK-47. On Aug. 12, officers shot and killed 24-year-old Nate Wilks when police say he turned toward them with a gun while they were chasing him.
"I think it's completely outrageous," protest organizer Yvette Felarca said. "The Oakland police are out of control because they're on a rampage and it's clear that the Oakland police are trying to act as judge, jury and executioner in each one of these instances."
Police officials say the incident was recorded by the officer's body camera and they are reviewing that as part of their investigation.
"Assaults on police officers are up significantly this year," said Whent. "It's a very difficult time in this country to be a police officer."
Police said at the time it is unclear how old the man is, but he appears to be in his 20s. Neighbors told ABC7 News it is possible he may have been mentally disabled.
Bay City News contributed to this story.