Officer Frank Bonifacio said the shooting occurred in the 1000 block of 88th Avenue at about 9:45 a.m. after someone in the area flagged down two police officers who were on patrol and told them that a nearby man was armed with a knife and acting erratically.
The officers got out of their car and spotted the man holding a knife in the middle of the street, according to Bonifacio.
A confrontation ensued and one of the two officers shot the man, Bonifacio said.
The shooting victim was identified by relatives as 28 year Corey Pollard.
"He's a very family-oriented man; has three small children," said Jenaeya Paul-Taylor, who told KTVU she is Pollard's cousin.
Paul-Taylor said her cousin suffers from bipolar disorder.
"He lives for his children. For officers to act in this manner, I think they didn't follow protocol and there should be an investigation," said Paul-Taylor.
Both officers were in police uniforms and were in a marked police vehicle, he said.
One of the officers is a rookie and the other was his field training officer, Bonifacio said. However, he didn't know which officer fired his gun.
Both officers were equipped with body cameras but investigators haven't yet determined if the incident was recorded, according to Bonifacio.
The officers have been placed on paid administrative leave, which is standard protocol in officer-involved shooting.
The shooting will be investigated by the Oakland Police Department's homicide and internal affairs units as well as the Alameda County District Attorney's Office.
Oakland police officers went 20 months without shooting at a person but Friday's incident marks the second officer-involved shooting in the city in less than a week.
Early last Saturday morning an officer shot at a man in the 2100 block of East 17th Street after the man allegedly swung golf clubs at the officer and a second officer. However, the officer's shot didn't hit the man, who was then arrested.
Police responded to that area after a parent called them and said their son was mentally disturbed and was armed and threatening to injure family members.