DENVER – For more than a decade, daredevils in snowsuits climbed atop their quarter-ton snowmobiles, sped them up icy ramps and flipped them head over heels into the frosty night air. Fans of action sports cheered while others, less enthralled with the event, wondered whether the sport was a good idea.

It’s a question that’s getting a much more serious look after last month’s Winter X Games, where things went wrong in a serious and tragic way.

One rider, with very little experience on snowmobiles, flew off his vehicle and the machine went careening into the fence, dangerously close to spectators. Another wrecked and separated his pelvis. That rider’s brother, 25-year-old Caleb Moore, lost control, landed on his head and, four days later, died from injuries related to the accident.