Snowmobile rider Caleb Moore died Thursday morning, a week after crashing during the Winter X Games in Aspen, Colo.

Moore, 25, was attempting a backflip last Thursday when he ended up going over the handlebars and face first into the snow. The 450-pound snowmobile then rolled over him. After staying down for a while, Moore walked off with help and was taken to the hospital. The Texas native developed bleeding around his heart and other complications.

Moore’s brother, Colten, also was injured in a crash last Thursday, suffering a separated pelvis.

X Games officials promised a thorough review of freestyle snowmobiling events following the first death in the 18-year history of the games.

“For 18 years, we have worked closely on safety issues with athletes, course designers and other experts,” organizers said in a statement. “Still, when the world’s best compete at the highest level in any sport, risks remain.”