The sheriff's office received a report of a shooting at 11:08 a.m. in the area of Rollingwood Drive and Fordham Street, Lee said.
Deputies arrived to find two shooting victims, a male and female. Both victims were taken to John Muir Medical Center in Walnut Creek, one by helicopter.
The victims were in a vehicle when a silver or white Nissan Frontier pickup truck drove past them and someone inside fired numerous shots, Lee said.
The man was shot in the head and the woman, who was pregnant, was shot in the ankle.
Some neighbors saw what happened and one woman recalled, "I heard two, three or four shots. At least three. I saw that car pull off there and a lady got out and ran around to the driver's side."
The 24-year-old man is in serious condition. The woman was treated and released.
Deputies are still searching for the shooters.
ABC7 contributed to this report.