At around 2:30 p.m. on Saturday, officers responded to several calls reporting shots fired in the area of Santa Clara and Capitol streets, according to Vallejo police.
Arriving officers found Mica Williams, of Vallejo, unconscious behind the wheel of a black Nissan Maxima that crashed into a parked vehicle and a street sign, police said.
Williams had suffered a single gunshot wound to his upper torso and was taken to a hospital in grave condition, police said.
He later succumbed to his injury, police said.
No suspect information has been released and a motive for the fatal shooting remains under investigation.
Anyone with information is urged to contact Vallejo police at (800) 488-9383.