One climber died and another was seriously injured after the two-person team fell around 1,000 feet while climbing a mountain in Alaska’s Denali National Park, officials said Friday,

The fall off Mount Johnson occurred Thursday night, the National Park Service said in a statement.

The climbers were roped together and climbing the 5,000-foot route known as “the Escalator” when they fell, the park officials said.

Their names were not released. The second climber suffered “serious traumatic injuries,” the park service said.

Another climbing party witnessed the fall, called it in at around 10:45 p.m. local time, and then went down to help, officials said.

They built a snow cave to help the surviving climber until a rescue helicopter and mountaineering rangers reached them at around 7 a.m. Friday, the park service said.

Mount Johnson is around 8,400 feet tall. The route the climbers were on is a steep technical alpine climb on the mountain’s southeast face, officials said.

The injured climber was flown to Talkeetna, south of the national park, for medical care and a helicopter later Friday retrieved the dead climber’s body, the park service said.