Authorities say a 31-year-old Denver man died after he slipped and fell while climbing a boulder in northern Colorado.

Boulder County sheriff’s officials say the man, whose name has not been released, was hiking with his girlfriend near Navajo Peak on Saturday afternoon when he fell 20 to 30 feet (6 to 9 meters) and landed in a rocky crevasse. The woman, who is a doctor, says the man hit his head several times during the fall and had no pulse when she climbed down to help him.

She did not have cellphone service and had to hike about 5 miles (8 kilometers) to Brainard Lake to report the fall. Investigators say she has been cooperative and they do not suspect foul play.

Navajo Peak is about 40 miles (64 kilometers) northwest of Denver.