The shooting happened around 4:00am this morning on University Avenue near Howe Avenue.
Police say a security guard approached three men gathered around a vehicle. The men reportedly jumped in their car, then raced right at the guard who pulled his gun and fired into the car.
The 19-year-old victim was taken to the UC Davis Med Center but he has died..
Police say it appears the security guard fired in self-defense but they are continuing their investigation.
Two other men in that car have been taken into custody.