(video below) Accident at the 0:55 mark, and short video also included. Caleb Moore was initially diagnosed and treated for concussion after the accident. He was 25.

Moore, a native of Krum, Texas, competed on all-terrain vehicles since his childhood before trying snowmobiles four years ago.

Family spokeswoman Chelsea Lawson released a statement announcing Moore's death, which occurred Thursday morning. The family declined to release any other details of his injuries.

It is the first death in the 17 years of the Winter X Games.

Moore suffered a concussion and was taken off the course during the snowmobile freestyle final at Buttermilk Mountain in Aspen, Colo., on Jan. 24.

While he was being evaluated, Moore was found to have bleeding on his heart and was airlifted to St. Mary's Hospital in Grand Junction. He had emergency surgery there on Friday. A family spokeswoman announced on Sunday that he'd suffered a "brain complication."

Moore was the first to make a run in the freestyle competition, in which riders navigate their 450-pound snowmobiles over a series of jumps in 75 seconds.

Attempting a backflip late in the run, Moore under rotated his sled and it did not get far enough down the landing ramp. The snowmobile's skis planted atop the ramp, knocking Moore off. After rotating 360 degrees, the skis of the sled landed on Moore as he slid down the ramp.

"It's definitely a scary thing for a sport like ours," said snowmobiler and X Games competitor Levi LaVallee on Tuesday. "The only thing we can do is we can look at that and learn from it and look at how we can try to prevent that.

"Other than that, you look at it, what happened to him, was an accident. He's done that trick multiple times. He's practiced. He's done everything he can to prevent that."

Added Daniel Bodin, a fellow competitor and Moore's close friend, "Ten years ago we didn't have foam pits, and it was just a couple of guys who had the foam pits. So everything is much safer now days. But still we keep pushing harder and harder, and everyone wants that gold medal. Everyone wants to be the best in the world. We're trying as much as we can … It's tough out there. We're just pushing so much."

ESPN released a statement Tuesday that said, "We've worked closely on safety issues with athletes, course designers and other experts for each of the 18 years of X Games. Still, when the world's best compete at the highest level in any sport, risks remain. Caleb is a four-time X Games medalist who fell short on his rotation on a move he has landed several times previously."

Moore was knocked unconscious in the crash and medical staff attended to him while he lay in the snow. When he awoke, he was able to answer questions and walked away from the hill.

In an interview before the race, Moore told the New York Times that he estimated he'd had 10 concussions.

Moore and his younger brother, Colten, began competing on snowmobiles four years ago after years of ATV racing. They entered their first X Games in 2010 after only about a month of practicing on snowmobiles.

At the 2010 X Games, Caleb Moore took bronze in the freestyle competition. He repeated that in 2011 and took silver in best trick that year.

He got bronze in the freestyle in 2012, while Colten Moore, 23, won gold.

Colten Moore also crashed during Thursday's competition, separating his pelvis.

After his sons were injured in Aspen, Wade Moore told the New York Times, "This is not new to us. You know it can happen at any time. We just hope it doesn't happen here, on this night."

Caleb Moore's death and other crashes in the snowmobile competition raise questions about the safety of the sport.

In Aspen last week, Bodin crashed during the freestyle competition – during which competitors perform mid-air tricks over a series of jumps – but was not injured and returned to win gold in the best trick final.

On Sunday, a young male spectator was hurt during that competition as a runaway snowmobile crashed into a group of fans. The fan was examined by X Games medical staff and released to his father. He was not hit by the snowmobile. http://www.liveleak.com/view?i=cad_1359347510