Three other youths carried Oscar Gallegos to the front of the Denny's in the 1000 block of Camino del Rio South about 10:15 p.m. Tuesday, asked employees at the eatery to call for paramedics and drove off, leaving the boy behind, according to San Diego police and the county Medical Examiner's Office.

The teen, address unknown, died of a chest wound at the scene a short time later, SDPD homicide Lt. Ernie Herbert said.

Detectives soon tracked down and interviewed the person who had been driving the vehicle that brought the victim to the restaurant. The investigation led to a trail of blood at Franklin Avenue and South Bancroft Street in the Mountain View area, where the fatal assault apparently occurred.

The motive for the slaying remains unknown, and police have announced no arrests in the case.