The Santa Clara County medical examiner’s office has identified the 15-year-old boy who was killed Friday in Cupertino after apparently climbing onto a tow bar connecting two gravel trailers being hauled by a tractor-trailer.The California Highway Patrol is still searching for the driver of the truck that ran over Javier Loyola Leon of Sunnyvale on Friday afternoon. CHP spokeswoman Brandie Dressel said the driver may have been unaware the boy had jumped onto his vehicle.Loyola Leon was walking on the east side of Wolfe Road around 12:30 p.m. when he encountered the tractor-trailer stopped at a red light, witnesses told the CHP. For some reason he climbed onto the tow bar connecting two trailers full of gravel.When the light turned green, the truck accelerated onto the southbound onramp for Interstate Highway 280 and Loyola Leon either jumped or fell from the tow bar. The truck ran him over, killing him instantly according to the CHP.Anyone who witnessed the incident, or has information on the tractor-trailer and its driver should contact the CHP at (408) 467-5354, ext. 271.