One man has been arrested and another remains outstanding in connection with the shooting, which was reported around 5 a.m. near the intersection of Donegal and Dublin drives, Vallejo police Lt. Ken Weaver said.
A neighbor heard glass breaking in a vehicle and called police. Officers arrived to find a Ford Tempo with the woman inside dead from apparent gunshot wounds, Weaver said.
As officers were responding to the scene, two suspects were spotted fleeing the area on foot, he said.
Police surrounded the neighborhood, and one of the men was found hiding in a residential backyard about two hours later and was arrested, Weaver said.
The other suspect remains on the loose. He is described as a black man who is about 25 years old, has dreadlocks, and was wearing a T-shirt and jeans, according to Weaver.
A motive for the shooting has not yet been determined, he said.
The homicide comes almost exactly 24 hours after a similar one elsewhere in the city.
At about 5 a.m. Friday, Enrique Alejandro Jimenez was found fatally shot in a white Ford Bronco on Admiral Callaghan Lane, located just off of Interstate Highway 80.
Jimenez, 23, of Vallejo, was apparently shot while he was waiting to be picked up to go to work, Weaver said.
"He was waiting for his boss, they carpooled together," he said. No arrests have been made in connection with the shooting and no suspect information was available today.
The shootings on consecutive days are Vallejo's first two homicides of 2011, Weaver said.
Anyone with information about either shooting is asked to call Vallejo police at (707) 648-4321.