Ueli Steck, one of the most feted mountaineers of his generation, died Sunday in an apparent fall in Nepal.

“Ueli Steck was killed while trying to climb Mount Everest and the Lhotse,” the family said on his Facebook page. The family added that the exact circumstances of his death were not immediately known.

“As soon as there are reliable findings on the causes of Uelis Steck’s death, the media will be informed,” the statement said. “The family asks the media for understanding that they will not provide any further information at the time.”

The Swiss climber, 40, was on Everest to acclimatize before attempting to summit the world’s tallest peak in May, using a never before climbed route. Everest and neighboring peak Nuptse share a common ridge, which is where Steck apparently slipped and fell.

Steck held several records for solo and speed climbing. He twice won the Piolet d’Or — Golden Ice Axe — a prestigious international mountaineering award. His accomplishments won him the moniker “Swiss Machine.”

He had long been sponsored by Mountain Hardwear but he’s no longer listed on the brand’s athlete’s web page.

His was the first casualty of the Everest climbing season.