The incident occurred around 1 a.m. Family members say Justo Quintero, 31, was on his way home from a bachelor party when he stopped along Arroyo Verde Road.
According to the L.A. County Sheriff's Department, which is investigating the incident, Quintero, who detectives say was armed, and the campus officer got into some sort of confrontation when the gun fire erupted. Family members say it apparently involved the volume of Quintero's music.
Quintero then reportedly fled the location in a vehicle before colliding with a parked vehicle.
South Pasadena police responded to the area and detained the suspect, who was suffering from gunshot wounds to the upper torso. He was transported to a local hospital but was later pronounced dead.
The officer suffered minor injuries and was treated at the scene.
Investigators say the suspect's handgun was recovered at the scene.
Family members say Quintero had been drinking, but say he wasn't a troublemaker or a gang member. They have no idea what sparked the shooting.
Anyone with information about the incident is encouraged to call the Sheriff's Homicide Bureau at (323) 890-5500.