The driver, who fled from the scene of the collision, was later stopped by sheriff's deputies and detained. The driver's name has not been released.
One victim died in hospital, another was treated on scene and released. A park ranger performed CPR on one of the victims until help arrived.
This is now a murder investigation, however, police say they won't release any details about the suspect. They believe the two pedestrians were hit in different parts of the park.
Officials say everyone involved are adults. Police say by the time they apprehended the suspect, her vehicle was already damaged with a broken windshield.
The suspect was taken to a local hospital for precautionary measures and will be later transported and booked into the Main Jail in San Jose.
Rancho San Antonio Open Space Preserve will be closed for the rest of the day.
Bay City News contributed to this report.
Editor's Note: Sheriff's officials clarified on Oct. 4 that only one person was struck in the incident. Go here for the report from that day.