DENVER -- A 21-year-old Kansas man is dead after he tried to exit a sport utility vehicle through the passenger's side window and fell onto a highway in Keystone.

The Colorado State Patrol said Michael Armstrong of Bonner Springs, Kan., was in a white Ford Explorer with three other people just before 9 p.m. Sunday when he climbed part way out of the SUV, then lost his hold on the vehicle and fell onto U.S. 6, near St. John Road.

He slid on to the right shoulder where he came to rest.

Armstrong was airlifted to Saint Anthony's Central Hospital in Denver, but was later pronounced dead.

No one else was hurt.

The driver, 20-year-old Kendra Martinez of Broomfield, was cited for driving under the influence of alcohol and illegal possession of alcohol by an underage person. She and the other passengers were not wearing their seat belts, the CSP said.

The two others in the the vehicle were Jakeb Welter, 25, of Keystone and Beau Rice, 27, of Lowman, Idaho.