Officials say this all started with a traffic stop on Henry Road in Napa County.
The sheriff's office says a deputy saw the car parked around 11 p.m. Sunday and got out to speak with the driver.
The deputy then radioed that shots have been fired.
An investigation is ongoing, and officials say they aren't yet releasing details on what led the officer to fire her weapon.
The man in the car was killed. The deputy says the man did have a gun.
They have not identified the deputy.
Police say no one else was involved. There was no one else in the car and no witnesses in the very remote area.