Authorities said the officer was working on a homicide case when he noticed a suspicious person on a bicycle about 1:30 a.m. The suspect rode away, but the officer chased him to Philadelphia and Narda streets.
The shooting occurred when the suspect allegedly reached for a gun during the confrontation. Police said he was struck once.
The suspect, whose name was withheld, was taken to the hospital in critical condition. He was expected to survive. The officer was not hurt.
A handgun believed to belong to the gang member was recovered at the scene of the shooting.
"There was a reason that this individual didn't want to stop and it appears that he was armed at the time of the encounter with the officer," said Sgt. Bob Dunn of the Anaheim Police Department. "The gun was found at very close proximity, so at some point the gun was in possession of that individual."
Police said they have increased patrols in the area due to increased tension between two rival gangs after the murder of a 14-year-old documented gang member.
There was another officer-involved shooting last Wednesday when a suspect allegedly moved his hand toward his waistband while fleeing police in the alley of the 800 block of South Philadelphia Street. The officer fired one round but did not hit the suspect, who threw his handgun and surrendered without further incident.
That suspect, identified as Pedro Lara of Anaheim, is also a documented gang member. His loaded semi-automatic handgun was recovered.