The Army initially said two were killed, one was injured and one was missing. The missing man was found dead late Wednesday, and the injured man died on the way to the hospital Wednesday, said Lt. Col. John Clearwater, a spokesman for the command at Fort Bragg, N.C.
All were male soldiers from Fort Campbell, Ky., he said. Their names haven't been released.
The crew was training in high-altitude mountainous conditions, "much like the environment they operate in Afghanistan," Clearwater said, adding that he didn't know whether the crew had served there.
The helicopter was assigned to the 160th Special Operations Aviation Regiment (Airborne) at Fort Campbell. Soldiers in the 160th are known as "night stalkers" because they specialize in nighttime operations. The regiment's Web site says the 160th has carried out combat operations in Iraq and Afghanistan.
Wednesday's flight began at Peterson Air Force Base in Colorado Springs, which is about 90 miles east of Mount Massive.
The cause of the crash hasn't been released. The Black Hawk's flight recorder was recovered and an investigation team from Fort Rucker, Ala., was at the crash site Thursday, Clearwater said.
The MH-60 Black Hawk is frequently used for infiltration missions and to bring supplies to special operations forces in the field, according to the unit's Web site. The helicopter is also used for rescue and medical evacuations, and an armed version is used for escort and fire support.
Not all helicopters can fly at high altitudes. That's because the air is thinner, requiring a more powerful helicopter to achieve the lift needed to stay airborne.
The soldiers should have had supplemental oxygen at that altitude, said Brian Cutler, assistant chief pilot at Guidance Helicopter Inc., a civilian helicopter training school in Prescott, Ariz. But he said the Black Hawk performs well in mountainous terrain.
"It's pretty well equipped for flying at that altitude," said Cutler, who doesn't have a military background.
The weather in Leadville, just east of Mount Massive, was clear Wednesday afternoon. The wind was gusting at about 26 mph, which is typical for the area.