Alexander Pancoe recently fought chronic myeloid leukemia and was attempting to climb Makalu to raise funds for a pediatric blood cancer program at a Chicago hospital.

"The two had just finished dinner and were settling into their sleeping bags, chatting casually, when Alex suddenly became unresponsive."

An American climber has died after attempting to scale the world's fifth-largest mountain. On Tuesday, Nepalese officials confirmed the death of 39-year-old Alexander Pancoe on Mount Makalu. Pancoe died on Sunday after suffering cardiac arrest while descending from Camp Three to Camp Two on the mountain.