HULETT, Wyo. (AP) — A climber fell to his death while rappelling down Devils Tower, leaving his partner stranded without a rope on the face of the Wyoming geological formation.

The stuck climber was rescued unharmed after crying out for help Sunday evening, Devils Tower National Monument Superintendent Doug Crossen said Wednesday.

The death of Stewart Phillip Porter, 21, of Eau Claire, Wisconsin, on Sunday, was the seventh climbing fatality in the park’s 118-year history. Some 6,000 people climb the formation every year.

The two were on a relatively easy climbing route called El Cracko Diablo. They had summited the tower and were headed back down when Porter fell.

How the fall happened was unknown. The accident was still being investigated, Crossen said.

Standing with sheer sides almost 870 feet (265 meters) above the surrounding countryside and a mile (1.6 kilometers) above sea level, Devils Tower is the world’s largest example of columnar jointing — fused pillars of igneous rock that formed as underground magma.

Established in 1906, Devils Tower was the first national monument and played a role in the 1977 film, “Close Encounters of the Third Kind.”