LOS ANGELES >> Authorities are poring through video to figure out how a confrontation between an off-duty Los Angeles police officer and a man described by family as mentally disabled ended in a shooting in a Costco store that killed the man and critically wounded his parents.

The officer opened fire after Kenneth French, 32, of Riverside, attacked him without provocation as the officer held his young child Friday night, according to police in Corona, about 40 miles east of LA.

The officer was the only one who fired shots, striking French and two of his family members, police said.

Authorities did not respond to requests for more information about what led to the attack and whether anyone but the officer had a weapon. They have not released the names of the officers or those wounded.

Rick Shureih, French’s cousin, told the Press-Enterprise in Riverside that French was a “gentle giant” who had mental disabilities. He declined to give specifics about his mental condition.

French was “non-violent, non-aggressive, non-verbal,” Shureih said, and “he has to be pretty much monitored.”

“He’s not the kind to trade words, so I don’t believe that a verbal confrontation happened,” Shureih said.

He said French’s parents, Russell and Paola French, were the others shot and that they were in intensive care Sunday.

The family is seeking an attorney, said Shureih, who posted a photo of French and his parents on Facebook.

“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,” Shureih wrote Sunday. “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!”

Los Angeles police have started an internal investigation, while Corona police and the Riverside County district attorney’s office investigate the shooting separately.

The LAPD said that it had no further information. Corona police and prosecutors did not respond to requests for comment Sunday.

Los Angeles Police Commission President Steve Soboroff said it is Chief Michel Moore’s decision whether to put the officer on leave, but it wasn’t clear if that happened.

The officer was treated and released at a hospital, and his child was not injured.

Off-duty officers can carry concealed weapons as long as they are authorized for on-duty use, according to the LAPD manual.

Joseph Giacalone, a professor at the John Jay College of Criminal Justice and a retired New York City police sergeant, said it’s justifiable to use deadly force even in a crowded store if the attacker has a weapon.

“If the guy pulled out a pocketknife and approaches him, game over,” Giacalone said.

Police have not said if French had any weapons or if the officer identified himself as police before firing.

Giacalone said video footage from Costco’s cameras and shoppers’ cellphones will be critical to the investigations.

While it’s not unusual for police to delay releasing information, such as an officer’s name, after a shooting for safety reasons, Giacalone said it’s important to get details out as quickly as possible.

“People start filling in the timelines for you” in the meantime, he said.

The shooting prompted a stampede of frightened shoppers, some who fled the store as others sought cover inside.

Witnesses reported seeing an argument between two people near a freezer section when at least six shots rang out.