Four climbers said to be old chums died on Mt. Everest this past weekend. Reports so far are that all four died from altitude sickness.

The climbers come from Germany, South Korea, Canada and China, Discovery News reports today. The climbers were part of a larger group of old high-school classmates who were planned to celebrate the 50th anniversary of their old school by climbing the world’s highest peak.  Read more: Mt. Everest.