At about 0540 Mountain time, the airplane impacted terrain, fatally injuring the private pilot and passenger. The two regularly flew the route as commuters. Instrument conditions prevailed. A witness saw an airplane flying low in the vicinity of the departure airport at about 0530. She described light snow falling; the snow became heavy shortly thereafter and, as she crossed a ridgeline, she spotted a fire burning north of the highway and called 911. Emergency responders arrived and identified airplane wreckage in the fire.