Laura Kraegel/KUCB

Officials at Unalaska's Fire and Public Safety Departments said they couldn't determine the cause of Tuesday's avalanche that killed 21-year-old snowmachiner Trey Henning.

But according to Acting Fire Chief Mike Hanson, there was significant new snowfall on the mountain near the Overland Drive quarry, where Henning was riding alone at the time of the accident.

Hope McKenney/KUCB

Updated 2/25/20 at 9:20 p.m. 

An Unalaska man was killed in an avalanche Tuesday evening while he was snowmachining in the Unalaska Valley.

Trey Henning, 21, was buried in the avalanche and later recovered from the site near the quarry on Overland Drive. In a statement, the Department of Public Safety said life-saving measures were unsuccessful.