Paul Walker -- best known for his role in "The Fast and the Furious" movies -- died Saturday afternoon after a single-car accident and explosion in Southern California ... TMZ has learned.
The accident happened in Santa Clarita -- north of Los Angeles -- and Paul was the passenger in the two-seater Porsche Carrera GT when the driver somehow lost control and slammed into a post or a tree ... and the car burst into flames.
Several of our sources -- some of whom were at the scene of the accident -- tell us a friend of Paul"s was driving and was also killed in the fiery wreck.