Otari, Japan - The sports world is mourning US skiing champion Kyle Smaine, who was killed in an avalanche in Japan, where the athlete had spent the past 10 days being photographed on the slopes, according to photographer Grant Gunderson.

"Yesterday was my absolute worst nightmare scenario," Gunderson explained on Instagram Sunday.

According to the photographer, he, Smaine, and a third skier were enjoying the last day of an adventure at the Tsugaike Kogen Ski Resort that left him too tired to join his partners for another run.

Gunderson was out of harm's way when he said an avalanche triggered by a skier from another group produced an "air blast" that tossed Smaine more than 160 feet to his death.

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The father of the 31-year-old skier from Lake Tahoe, California, confirmed to NBC News his son – who won the halfpipe FIS World Ski Championships in Austria in 2015 – died in the avalanche.

Smaine had revealed on Instagram Saturday that "Unbelievable snow quality, non-stop storms, and really fun terrain" were his reasons for going to Japan every winter.

That post, which included video of Smaine in action, later became an online memorial.

A third member of their party, identified on Gunderson's Instagram post as Adam, was buried under five feet of snow for 25 minutes, but emerged unharmed.

A second, unnamed skier was killed in Saturday's tragedy despite the efforts of first responders, according to Gunderson.