Snowmobiler Caleb Moore died Thursday as a result of injuries he suffered in a crash in the X Games one week ago. 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 Winter X Games, which had its 17th edition in Aspen last week.

"We are deeply saddened by Caleb Moore's passing and our thoughts and prayers go out to his parents, Wade and Michelle, his brother, Colten, and the entire Moore family," ESPN said in a statement released Thursday. "He will be remembered for his natural passion for life and his deep love for his family and friends, and he will always be an inspiration to everyone he touched in the action sports community."

ESPN added that it will conduct a thorough review of the snowmobiling discipline and adopt any appropriate changes. The company says it works closely on safety issues with athletes and other sports experts.

"Still, when the world's best compete at the highest level in any sport, risks remain," the statement said. "Caleb was a four-time X Games medalist attempting a move he has landed several times previously."

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."

Caleb Moore died at the age of 25 on Jan. 31, 2013, due to complications of a snowmobile crash at the X Games one week earlier. Eric Lars Bakke, AP Fullscreen

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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."

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.

Bodin, who is from Sweden, said he has known the Moore brothers for three or four years. "He's very motivated," Bodin said of Caleb Moore. "If he really wants something, he's a hard worker. Whatever it takes to get a medal."

He also spoke of Caleb Moore's "big heart. He's been helping me out, not really getting anything back. He just likes to help people."

Bodin spent time training with the brothers in Texas before the X Games and then at Electric Mountain Lodge in Colorado. The friends would support each other when traveling through the United States and Europe to compete.

"This year we decided to work together," Bodin said. "I fly over to his house and things were going well. It's just so crazy… I still can't believe what's happened here."

A Give Forward web site that has been set up to raise money for Moore's medical bills topped $26,000 by mid-day Thursday. Australian Jackson Strong is auctioning the snowmobile he used during the X Games on eBay to help raise money for the family. As of Thursday afternoon, the bidding stood at $8,900.