The incident happened during a daytime heroin bust the Fontana Police Department was conducting in the city of Ontario.
According to the District Attorney's Office, Corporal Keith Zagorian ordered Isiordia eight or nine times to show his hands. But instead, the suspect moved his left hand toward the back of his waistband. Zagorian thought he had a gun so he fired four rounds at Isiordia.
The suspect was later determined to be unarmed.
An autopsy revealed that Isiordia died from multiple gunshot wounds to his chest and abdomen.
Zagorian has been with the Fontana Police Department for four years and has worked hundreds of narcotic-related cases.