A driver was killed early Monday morning in Douglas County when his vehicle flew down an embankment and into Castlewood Canyon creek.

Police responding to the scene at 2 a.m. found the vehicle in the creek near Castlewood Canyon and Highway 86 and the man's body underneath the vehicle. A motorist who was following the Chevy 3500 pickup truck saw the truck go over the cliff and called 911.

The driver was identified as 24-year-old Terry Walker of Franktown, Colo.

Investigators said the truck was traveling southbound on Castlewood Canyon Road in Castlewood State Park when it lost control on the narrow winding dirt road. The truck went off the left side of the road and plunged vertically into the bottom of the canyon, police said.

Authorities believe the truck fell 400 feet.

Walker was not wearing a seat belt and was ejected from the truck, investigators said.

They are trying to determine if speed or alcohol were factors in the crash.