Jorge Herrera was riding in the eighth and final race of the day when he was thrown from his mount. Herrera's horse, 4-year-old Morito, reportedly clipped the heels of another horse, Tribal Sun. Morito then stumbled and Herrera was left on the ground with massive head injuries.
"He was trampled by his horse or another horse," Alameda County Fair spokesperson April Mitchell said.
Mitchell says paramedics tended to Herrera right away.
"As our normal safety protocol dictates, we had an ambulance that was following the race so emergency personnel responded immediately," she said.
But Herrera was unable to survive the accident. He died two hours later at Eden Medical Center in Castro Valley.
The 33-year old jockey was said to be relatively new to the horse racing industry. According to Equibase.com, Herrera had 55 wins and nearly $700,000 in winnings throughout the course of his career.
Fair organizers say this is the first time a jockey has died here since 1975.