SOUTH EL MONTE, Calif.—The Los Angeles County Sheriff’s Department is circulating a photo of a 16-year-old boy who went missing in South El Monte and is also a person of interest in a recent fatal hit-and-run crash in Rosemead. Mariano Coc went missing from his South El Monte home on Nov. 7, the sheriff’s Temple station reported. Detectives also believe that he may be the victim of a crime. Coc was the last person seen with a 2009 black Nissan Altima with a gray bumper that was involved in a fatal-and-run crash Monday in Rosemead. It occurred at about 10:30 a.m. that day in the 2700 block of San Gabriel Boulevard, near the intersection of Garvey Avenue, and escalated into an argument between two people. Riverside resident Haiou He, 61, exited his vehicle to speak with the other vehicle’s driver, when that driver allegedly put the vehicle in reverse and …