The shooting happened near Imperial Highway and Paramount Boulevard about 7:30 p.m. Saturday.
Officers received a call about an armed robbery in the area. Officials said responding officers found Michael Nida wearing clothing that matched a suspect description and behaving in a suspicious manner. They detained Nida, but he escaped and ran into the yard of a nearby house.
As officers surrounded the area, Nida tried to flee again but was caught. That's when Nida fled yet again, leading officers on a short foot chase.
Police said that during the chase, Nida turned toward the pursuing officers in an aggressive manner. Authorities said an officer feared Nida was armed and shot him.
"He felt that the suspect's actions were dangerous and he feared for the safety of everybody around him, including some civilians, and he fired at the suspect," said Lt. Dave Dolson of the Los Angeles County Sheriff's Department. "
Nida, 31, was taken to the hospital, where he was pronounced dead.
No weapon was found.
Sheriff's investigators said it appears Nida was not involved in the robbery. They were trying to determine whether the officer-involved shooting was connected to the robbery of a woman at a nearby ATM machine moments earlier. Another suspect in that robbery got away.
"I just seen my husband get gunned down by the Downey police for no reason. They didn't have the evidence to do that," said Nida's wife, Nally Nida. "I just want justice for my husband, for my kids."
Nida's family said police had the wrong person. They said he had crossed the street to go to a tobacco shop after stopping to buy gas with his wife.
They claim he was shot five times, including twice in the back. Investigators said only three rounds were fired.
"Downey police, they need training. They are out of control," said Terri Teramura, Nida's sister. "Our family is grieving now. Michael has four kids. He was only 31 years old. His birthday is on Tuesday."
Investigators will present their findings to the District Attorney's Office to determine if the shooting was justified.