ROCKY MOUNTAIN NATIONAL PARK (CBS4) – A park volunteer died after falling while descending a 13,000-foot-tall mountain in Rocky Mountain National Park.

Ken Teselle, 73, was off-duty when he fell while going down Mount Lady Washington above Chasm Lake.

The trail to Chasm Lake (credit: Brian Denning of Broomfield)

Bystanders who witnessed the fall Wednesday morning tried to help, as did park rangers who arrived on scene 15 minutes after being contacted.

They performed CPR, but Teselle was pronounced dead at the scene.

Due to the location and weather conditions, rangers stayed in the area Wednesday night and were going to begin recovery efforts Thursday.