According to the authorities, a man was drunk when he found himself behind the wheel accused an officer, who was then shot dead during the interruption of the traffic. The resident said Friday, according to Sgt's Stanislaus County Sheriff Tom Letras, that he had not seen the police officer.
Ronil Singh parked the vehicle, but heard the shots a few minutes later.
The suspected man was arrested the time he was preparing to flee to his native country, Mexico.
Stanislaus County Sheriff Adam Christianson said at a press conference that the massacre could have been avoided if California's law on sanctuaries had not prevented local authorities from denouncing Perez Arriaga - a gang affiliate - immigration officers after two previous arrests.
But a spokesman for Gov. Jerry Brown said the law allowed for sharing information about dangerous gang members with federal authorities.