The death Thursday of 25-year-old snowmobiler Caleb Moore following a crash last week in Aspen was the first in the 18-year history of the X Games.
His family issued a statement saying they're grateful for all the prayers and support they have received from people around the world.
X Games officials expressed their condolences and said Moore, a four-time X Games medalist, would be remembered "for his natural passion for life and his deep love for his family and friends."
The Twitter accounts of many athletes from a wide range of sports expressed their sympathy Thursday:
New York Jets quarterback Tim Tebow: "So sad to hear about the passing of snowmobiler Caleb Moore. My prayers go out to his younger brother Colten & their entire family."
Freestyle skier Kaya Turski: "The spirit of Caleb Moore will be floating among us forever. RIP."
Surfer Kelly Slater: "Tragic. Don't even know what to say."
Snowboarder Gretchen Bleiler, Tampa Bay third baseman Evan Longoria, motorsports standout Travis Pastrana and NASCAR driver Austin Dillon were among others who tweeted their condolences.