Moore was attempting a backflip in the freestyle event when the skis on his snowmobile caught the lip of the landing area, sending him flying over the handlebars. He landed face-first into the snow, and his 450-pound snowmobile rolled over him.
Yakima, Wash.'s Joe Parsons was competing in the same event and won the silver medal. He says Moore's death is a tragedy, and he'll be looking into the safety of the sport.
"It's really unfortunate, and I hope his family can get through this. And as someone with some power in the sport, I'll do what I can to make it safer in the future," Parsons said.
Moore actually walked away from the crash but developed bleeding around his heart and a complication involving his brain.
Moore was a Texas kid drawn to the snow, rehearsing complicated tricks on a snowmobile into a foam pit back home until they became second nature and ready for the mountains.
With his younger brother following along and constantly pushing him, Moore became a rising talent in action sports.
Moore had been undergoing care at a hospital in Grand Junction since the Jan. 24 crash. Family spokeswoman Chelsea Lawson confirmed his death, the first in the 18-year history of the X Games.
"He lived his life to the fullest. He was an inspiration," Lawson said.
A former all-terrain vehicle racer, Moore switched over to snowmobiles as a teenager and quickly rose to the top of the sport. He won four Winter X Games medals, including a bronze last season when his younger brother, Colten, captured gold.
Moore stayed down for quite some time, before walking off with help and going to a hospital to be treated for a concussion. Moore developed bleeding around his heart and was flown to a hospital in Grand Junction for surgery. The family later said that Moore, of Krum, Texas, also had a complication involving his brain.
Colten Moore was injured in a separate crash that same night. He suffered a separated pelvis in the spill.
The family said in a statement they were grateful for all the prayers and support they have received from people around the world.
X Games officials expressed their condolences and said Moore 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: "Our world has lost another bright light. Sending my deepest condolences to the family and friends of Caleb Moore."
- Tampa Bay third baseman Evan Longoria, who made a visit to Winter X last weekend: "Tragic day for the family of Caleb Moore. Our deepest sympathies go out to all who he influenced and touched. RIP."
- Motorsports standout Travis Pastrana: "So sad to hear about Caleb Moore. My condolences and prayers go out to his family and friends."
- NASCAR driver Austin Dillon: "Just heard about Caleb Moore. I don't know what to say other than I'm praying for his family and friends. He was a true Action Sports Hero."
B.C. Vaught, Caleb Moore's agent for almost a decade, said he first saw Moore when he was racing an ATV in Minnesota and signed him up to star in some action sports movies.
Later, Moore wanted to make the switch from ATVs to snowmobiles and Vaught helped him. A natural talent, it only took Moore two weeks to master a difficult backflip.
Moore honed his skills in Krum, a town about 5,000 people 50 miles northwest of Dallas that rarely sees snow. Instead, he worked on tricks by launching his sled into a foam pit. After a brief training run on snow ramps in Michigan, he was ready for his sport's biggest stage - the 2010 Winter X Games.
In that contest, Moore captured a bronze in freestyle and finished sixth in best trick. Two years later, his biography on ESPN said, "Caleb Moore has gone from 'beginner's luck' to 'serious threat.'"
That was hardly a surprise to Vaught, who said, "Whatever he wanted to do, he did it."
Vaught said Moore didn't believe his sport was too extreme, but rather "it was a lifestyle." He was good at it - along with ATV racing - as he accumulated a garage full of trophies.
Still, Moore's death is sure to ignite the debate over safety of the discipline. Whether action sports are too dangerous is an issue that's been raised before.
When freestyle skier Sarah Burke died in a training accident a little more than a year ago in Park City, Utah, there were questions about the halfpipe. Before that, the sport was examined when snowboarder Kevin Pearce suffered a severe brain injury in a fall in the same pipe as Burke two years earlier. Pearce has recovered and served as an analyst at Winter X.
But in general, the athletes accept the risks and defend their disciplines.
"I just look at it like this: Yes, we're in a dangerous sport," fellow snowmobile rider Levi LaVallee said. "Anytime you're doing a backflip on anything, it's dangerous. But we're training to do this. This is what we practice, what we do day in and day out. We're comfortable with doing this stuff."
LaVallee recently described Moore as a "fierce competitor."
"A very creative mind," LaVallee said. "I've watched him try some crazy, crazy tricks and some of them were successful, some of them not so much. But he was first guy to get back on a sled and go try it again. It shows a lot of heart."
X Games officials said in a statement that they would conduct a thorough review of freestyle snowmobiling events and adopt any appropriate changes.
"For 18 years, we have worked closely on safety issues with athletes, course designers and other experts. Still, when the world's best compete at the highest level in any sport, risks remain," they said, noting that Moore was hurt performing a move he had done several times before.
The Associated Press contributed to this report.