Washington State Patrol Trooper Mark Francis said the accident happened at about 4:20 p.m. on Lummi Shore Road near Cagey Road.
Francis said four young men were in a Ford F150 extended cab truck when one of the men, 18-year-old Isaac O. Misanes, fell out of the back window, tumbled out of the truck bed and was run over by the truck.
Misanes died at the scene.
Francis said investigators do not believe drugs or alcohol played a role in the accident. Troopers are still trying to determine exactly how the accident happened.