What was the cause of Stefano Longhi's death as noted in the nonfiction book, The White Spider: The Story of the North Face of the Eiger?

Longhi was an Italian climber who, along with Claudio Corti, attempted to climb the North Face in 1957. Corti and Longhi headed up the wrong route, and once they were on the correct route, they found Nothdurft and Mayer also climbing. During the ascent, Longhi fell and became stranded. He died on the mountain before rescue could get to him.