Christopher Walker, 23, of Antioch, had worked at the department for two years, most recently providing security at San Francisco General Hospital, according to spokeswoman Eileen Hirst. Before that, he worked at the San Francisco County Jail.
According to Hercules police, Walker was racing a red Chevrolet Camaro against another car when he crashed into a light pole on Palm Avenue, between Sycamore Avenue and the state Highway 4 on-ramp, at about 2:30 p.m.
The other car, which left the scene of the crash, was described as possibly a newer model, four-door, silver Nissan Sentra with paper dealer plates, according to Hercules police.
Walker, who was alone in the Camaro, was pronounced dead at the scene.
Hirst said Walker was a third-generation deputy sheriff, whose mother is a sheriff's lieutenant and grandfather was a former lieutenant.
Walker left behind "many friends in the sheriff's department," said Hirst. "He was a very well-liked deputy and a very good deputy," she said. His family is planning a private memorial service.
Hirst said it was not known why Walker may have been involved in a street race.
"Because we're not the investigating agency, there's very little that we know at this point," Hirst said.
"It does appear that both vehicles were involved in inappropriate behavior," Hercules police spokeswoman Michelle Harrington said today.
"We do have one witness that was able to provide the description of the Nissan Sentra, and was able to say that they were speeding," Harrington said.
Harrington said the witness, however, was not able to identify the driver of the vehicle.
But because the crash area can be seen from Highway 4, there may be other witnesses, she said.
Anyone with information on the Sentra or its driver is asked to call Hercules police at (510) 724-1111.