Two accounts of the shooting that caused chaos inside the busy warehouse store on June 14 painted completely different pictures of the series of events, with both describing different parties as the victim.
Attorney David Winslow said his client - a Los Angeles Police Department officer whom he wouldn't name - was struck from behind without a word being spoken Friday night as he fed his son samples of teriyaki chicken in the store.
"There was no discussion, there was no argument, there was no warning at all," Winslow said. "He was suddenly struck, knocked unconscious. When he opened his eyes moments later, he was on the ground, on the concrete. With his son also on the concrete. His son was screaming."
"That's when he had no choice but to use deadly force."
The off-duty officer shot and killed Kenneth French, 32, of Riverside, and critically wounded French's parents. French's mother remains hospitalized in critical condition. His father is stable.
An attorney for the French family argued that a civilian involved in such an incident would have been arrested.
"French's family is particularly bothered by the fact that if anyone other than an off-duty police officer had shot three unarmed civilians in a Costco, that person would be in jail and facing criminal charges for murder," said attorney Dale Galipo, who represents the French family.
Corona police spokesman said during a news conference shortly after the shooting that witnesses had reported hearing an argument. A statement from the department the following day, however, did not mention a verbal altercation and said the attack was "without provocation."
Costco Shooting Community Update – A message from the City of Corona Chief of Police, George Johnstone.— Corona Police Dept. (@CoronaPD) June 18, 2019
Anyone who may have additional information regarding this case is encouraged to contact Lieutenant Newman at 951-817-5788 or email Robert.Newman@CoronaCA.gov pic.twitter.com/AkVuEcCvnx
The Los Angeles Police Department is conducting its own investigation into the incident and the officer remains assigned to home duty.
"It might be what we think one day is something different the next," said Mayor Eric Garcetti. "But we will get to the bottom of this matter. We will get the truth. There will be accountability and there will be justice."
A cousin of Kenneth French, the man who was killed, described him as a "gentle man" who didn't speak because of a mental condition.
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Rick Shureih, French's cousin, told the Press-Enterprise in Riverside that French was gentle and didn't speak because of a mental condition that started in adulthood. He did not provide details on the condition, but he said French had "to be pretty much monitored" and his cousin's parents, Russell and Paola French, accompanied him everywhere.
In a Facebook posting Monday, Shureih said the family has gotten "witness accounts that do not match up to the original story." He declined to provide details, saying the information is confidential. He also said the family is pro-police but wants justice and called on authorities to arrest the officer. The family's relatives are urging anyone who witnessed the deadly encounter to contact them.
Winslow said he was not aware French had a disability.
"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."
The officer - who has been with the LAPD for seven years and currently works in the Southwest Division - was interviewed Monday by LAPD investigators as part of the department's administrative probe, Winslow said. He is on paid administrative leave that is mandatory after an officer-involved shooting.
MORE: Off-duty LAPD officer fatally shot man at Costco in Corona, police say
The officer's head injury was caused by a "severe blow" and he was treated at the hospital, his attorney said. His child was not harmed.
Corona police did not respond to requests for information about Winslow's statements, what immediately preceded the shooting and whether anyone other than the officer had a weapon.
The Riverside County District Attorney's Office issued a statement urging the public to be patient. Once Corona police finish their investigation, prosecutors will review and consider whether to bring criminal charges.
Corona police say the only weapon recovered at the scene belonged to the off-duty officer.
Authorities have not said if the officer identified himself as a police officer before firing. An earlier statement by Corona police referred to the off-duty officer as a "victim."
Witnesses reported seeing an argument between two people near a freezer section when at least six shots rang out. The shooting prompted a stampede of frightened shoppers, some fleeing the store as others sought cover inside.
Video from Costco's security cameras and shoppers' cellphones will be critical to the investigations, said Samuel Walker, a retired criminal justice professor at the University of Nebraska at Omaha and an expert on police accountability.
Off-duty officers can carry concealed firearms as long as the guns are authorized for on-duty use, according to the LAPD manual. Regardless of whether they're in uniform, police officers are allowed to use deadly force in self-defense or defense of others if it's clear there is no alternative, said Robert Weisberg, a professor at Stanford University's law school.
The Associated Press contributed to this story.