His last words were:

“That guy’s got to stop. . . . He’ll see us.”

When James Dean died, only one of his movies, East of Eden, had been released. The other two, Rebel Without a Cause and Giant, had not. In fact Dean had just finished filming on Giant when he and a stuntman jumped into his new Porsche, named “The Little Bastard,” and sped off to a weekend racing event in Salinas, California. They were stopped by a patrol car near Bakersfield, and Dean received a ticket for speeding. Two hours later, while on a two-lane highway, Dean saw a car begin to turn onto the road ahead. When Dean’s Porsche slammed into the vehicle, it’s driver’s side was crushed. Dean was killed instantly, and his passenger was seriously injured when thrown out of the car. The driver of the other vehicle, a 23 year old college student, suffered only minor injuries.

-From Last Words of Real People

And:

“My fun days are over.”
(Shortly before his fatal car crash.)