Corona police said an off-duty officer was shopping Friday night, holding his young child, when he was assaulted by a man.
The officer shot and killed 32-year-old Kenneth French of Riverside and critically wounded French's parents.
MORE: Off-duty LAPD officer fatally shot man at Costco in Corona, police say
A resident in the French's Riverside neighborhood said Kenneth was not communicative and also had not showed any signs of violence.
"I don't know if he has autism, but he's not talkative," said Rahman Bace, who lives next door to the French family. "He doesn't even talk."
When outside walking, Kenneth would just keep his head down and not even say hello, Bace said.
He described Kenneth and his family as "sweet."
"They are the sweetest family you can find here."
Family members say the mother is in a coma and the father remains hospitalized.
One of French's family members posted on social media, saying they have witness accounts that don't match up with the original story, and want Corona police to review surveillance video from inside the Costco once again.
The officer involved has not been identified. The Los Angeles Police Department said it is launching its own investigation into the officer's actions.
The off-duty officer's lawyer told the Associated Press the officer was feeding his son samples inside the Costco when he was briefly knocked unconscious, and that the officer believed he was under attack.
The officer has been with the department for seven years and has been assigned to home while the investigation proceeds.
To the family's neighbor, the shooting was stunning.
"If you carry a gun, especially in California, you cannot be drawing your gun," Bace said. "You're an off-duty officer, for God's sake. What happens if you don't have the gun? Nobody would be dead, honestly."
French's cousin posted a picture on social media of French with his mother and father.
The cousin, Rick Shureih, claims his relatives have been made out to be suspects and the off-duty officer the victim.
Shureih posted on Facebook:
"I'm not keeping quiet about this! People need to know! This is my family! These are the victims of the Costco shooting the other night. My cousin Kenneth was killed and his parents, my aunt & uncle were also both shot and are in ICU. Do they look intimidating to you? Did he really have to shoot them all? I'm posting this picture because the stories on social media have made them out to be the suspects, and the off duty cop the victim. This is a family that was unarmed and was just grocery shopping. Truth will come out! I'm sure this was a misunderstanding that got escalated for no reason! If anyone was a witness please get in contact with us."
French was a "gentle giant" who was mentally disabled, Shureih told The Press-Enterprise. He said French and his family were unarmed at the time of the shooting.
Corona police say the only weapon recovered at the scene belonged to the off-duty officer.
An earlier statement by Corona police referred to the off-duty officer as a "victim."
The off-duty officer -- assigned to the LAPD's Southwest Station -- suffered minor injuries in the incident.
The shooting occurred at the store located at 480 N. McKinley Street. Multiple witnesses said they heard gunshots around 7:45 p.m. They said there was chaos after shots were fired. People ran to escape, but the doors were reportedly locked, which added to the panic.
Officials in Riverside County are also conducting a separate investigation.
The family's relatives are urging anyone who witnessed the deadly encounter to contact them.