CORONA (CBSLA) – A shooting involving an off-duty Los Angeles Police Department officer was being investigated Saturday after the officer reportedly fired his gun inside of a Costco Wholesale in Corona Friday, killing one person and injuring three.

Officers were sent to the scene at 7:46 p.m. after receiving calls of an active shooter inside, according to the Corona Police Department.

Witnesses said the gunfire started when two men got into an argument inside of the store.

“From my understanding, from some people we talked to, there was apparently an argument inside. Some type of argument that ensued into a gun battle,” Lt. Jeff Edwards told reporters.

Upon their arrival, officers reported finding one dead and three wounded, including the suspect.

According to CBSLA reporter Joy Benedict, the LAPD had “use of force” investigators at the scene all night as the department conducted their own investigation.

The off-duty LAPD officer reportedly works in the Southwest Division and shot and killed a man during an altercation after feeling threatened.

LAPD released a statement Saturday morning saying, “The Los Angeles Police Department has learned that one of our off-duty patrol officers assigned to Southwest Division was involved in a shooting in Corona Friday night. Our officer suffered minor injuries in the incident and was transported to a local hospital where he was treated and released. The Department has initiated an Administrative Investigation and is working with the Corona Police Department to learn more about the incident.”

The injured– including the off-duty officer — were transported to a local hospital.

Corona Police on Saturday identified the dead man as Kenneth French, 32, of Riverside. They also said French and the unidentified officer did not know each other. Police said French assaulted the officer while the officer was holding his young child.

The officer shot and killed French and critically wounded two of French’s family members. The officer was treated at the hospital and released.

Officials said the officer’s weapon was the only one used in the incident.

Witnesses at the scene told CBSLA reporter Nicole Comstock they heard an argument before hearing seven or eight shots.

The investigation is currently ongoing. The officer is not in custody as investigators look into what may have prompted the shooting including the possibility of self-defense.