A 24-year-old from Colorado was found “seated at the summit” of Bolivia’s second largest mountain after his lungs collapsed during a climb.

       Daniel Granberg died two days into the trek across Illimani, which is 21,004 feet (6,402 meters) in elevation and visible from La Paz, the Bolivian capital.

       Sergio Condori Vallejos, a mountain guide who works with Bolivian Andean Rescue, said Daniel was found “lifeless” and “seated at the summit”, which is part of Bolivia's Cordillera Real range.

       Mr Vallejos also told The Associated Press (AP), that Daniel had embarked on the longest and toughest route across the Cordillera Real range, and Illmani, before falling ill.

       He was accompanied by two guides who alerted rescuers to his death, before his body was carried down the mountain from an elevation of 20,391 feet (6,216 meters), which took two days.

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       His body was taken to a morgue at a hospital in La Paz.

       According to Daniel’s mother, Jean Granberg, her son was suffering from a shortness of breath the night before and had a mild headache, but nothing that indicated his life was at risk.

       Ms Granberg told the AP that her son died from high-altitude pulmonary distress, which can affect climbers at elevations above 8,000 feet (2,438 meters).

       Daniel had already been in Bolivia for two months, where he had climbed several of the Andean nation’s tallest summits, including Huayna Potosi, which is (19,973 feet )6,088 meters, his social media posts showed.

       His mother described him as being warm-hearted, well-travelled and adventurous young man, and said his family were touched by messages of support from his friends across the world.

       “But I, just as a mom, my heart's broken. Twenty-four years is not long enough and I just wish somehow there'd been some kind of warning,” said Ms Grenberg. “If he had felt like he was in danger in any way, he would have come down the mountain. But I think it happened so fast.”

       Daniel was said to have taught himself physics, and was described by his mother as being “the smartest person” she knew.

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       He left Princeton University to become a subcontractor for the US Department of Energy.

       Additional reporting by The Associated Press.