Quinn Boyer, the Santa Clara County paramedic who was shot while driving in the Oakland hills Tuesday, died Thursday afternoon at Highland Hospital, officials said.

Police are treating the case as a homicide and are investigating whether robbery was a motive.

Boyer, 34, was off duty and stopped at an intersection on the 5200 block of Keller Avenue about noon Tuesday when someone in another car got out and opened fire. Boyer tried to flee in his Honda Civic, but jumped the median and plunged into a ravine.

He was pronounced dead at 3:53 p.m. Thursday, police said.

He had worked as a paramedic since 2008.

Monica Gomez, a spokeswoman for Santa Clara County Ambulance, where Boyer worked for the past two years, said a memorial has been set up at the service's facility at 1345 Vander Way in San Jose.

"Our hearts are heavy with emotion, and we certainly want to extend our thoughts and prayers to his family and friends as they cope with this loss," Gomez said.

"Quinn was very well liked by all of his colleagues and was very dedicated in his role as a paramedic."

Chronicle staff writer Henry K. Lee contributed to this report.