"His friends were on the side watching him go across the mountain," Bridge said.
The snow slab started to shift underneath a cliff where unstable snow pellets had pooled, according to the Utah Avalanche Center. Baker was swept down the mountain into Dutch Draw, a basin to the southeast of the resort.
Bridge said Baker and the group he was with did not have any safety beacons and were in an area that was clearly marked with warning signs stating they were leaving a groomed trail area.
The area was wind-loaded with soft, dense slabs of new snow that started to slide at about 1 foot deep and 40 feet wide, but fanned out to about 150 feet at the bottom. The avalanche carried Baker down the mountain past small trees and debris before he was buried for about 40 minutes under 3½ feet of snow. His snowboard was broken in half, according to the Utah Avalanche Center
Friends and Summit County Search and Rescue and The Canyons ski patrol helped search for Baker and tried to dig him out of the avalanche, which was estimated to have travelled 900 feet.
Baker was flown by helicopter in "extremely critical condition" to University Hospital, where he was pronounced dead a short time after arriving at the hospital, Bridge said.
The Dutch Draw area is "hugely popular for out-of-bounds skiing and snowboarding," said Craig Gordon, forecaster for the Utah Avalanche Center.
The avalanche-prone terrain was under a warning of high danger Thursday, meaning that human-triggered avalanches are likely.
After a slide nearly missed skiers in 2009, the center reported "there have been several close calls in this area."
In January 2005, Idaho snowboarder Shane Maixner rode the Ninety-Nine 90 Express lift, then crossed through a resort gate before dropping into Dutch Draw and being buried in a massive avalanche that took his life.
On New Year's Day 2011, an avalanche was reported there, according to Utah Avalanche Center data.
"The winds were cranking all day," the witness wrote. "The slope fractured around me. I was able to reach [an] island of trees and let the slide run."