The head-on collision in Whitman County that killed one and injured five others was caused by a 21-year-old driver who fell asleep at the wheel, the Washington State Patrol said Saturday. Susie S. Koontz, 93, was declared dead at the scene on State Route 26 near LaCrosse, Wash. Koontz was riding in an eastbound Toyota Prius when a westbound Chevrolet Cobalt driven by Diana Chun drifted off the road and then swerved into the opposing lane and struck the Prius head on. Chun, of Coulee Dam, and her passenger Erick J. Quezada Bastida, 21, of Pullman, were taken to Whitman County hospital in Colfax. Also injured in the accident was the driver of the Prius, Mary E. Koontz, 59 of Seattle, who was airlifted to Kadlec Medical Center in Richland; and her passengers Cordelia E. Burris, 61 of Newcastle, and Judith A. Koontz, 63 of Bellingham, who were airlifted to Sacred Heart Medical Center in Spokane. The accident occurred around 5:30 p.m.