Life is slipping away from Texas snowmobiler Caleb Moore after a horrific crash Thursday night at Aspen’s Winter X Games. Family of the 25-year-old athlete gathered Monday at St. Mary’s Hospital in Grand Junction.

“Caleb is not doing good at all,” Caleb’s grandfather Charles Moore told The Denver Post Monday afternoon. “The prognosis is not good at all. It’s almost certain he’s not going to make it.”

If indeed Moore loses his fight, it will mark the first fatality in the 17-year history of the Winter X Games.

“Caleb is in critical condition and is being closely monitored,” family spokeswoman Chelsea Lawson said Monday evening. “The Moores want to express their gratitude to all of Caleb’s fans, friends and family for their strong support and ask for continued prayers in the coming days. The family will not be making any other public statements for the time being. Thank you for respecting the family’s privacy during this difficult time.”

Moore was injured Thursday evening during the snowmobile freestyle contest. He under-rotated a back flip and dug the skis of his sled into the lip of the landing.

The 450-pound, heavily modified Polaris snowmobile slammed Moore as he tumbled down the landing ramp, knocking him unconscious. When Moore came to, he was moving and asked his brother and fellow freestyle snowmobile competitor Colten what happened.

He was rushed to Aspen Valley Hospital with a concussion. Doctors there discovered bleeding around his heart and he was helicoptered to Grand Junction’s St. Mary’s Hospital. Doctors there performed emergency heart surgery Friday morning. Moore was recovering in intensive care for a heart contusion.

Late Sunday, a family spokeswoman said the cardiac injury led to “a secondary complication involving his brain.”

Moore and brother Colten stormed the snowmobile freestyle scene three years ago in Aspen, transferring their decades of experience racing and jumping ATV four-wheelers to snow sports. The duo learned to flip snowmobiles in a foam pit they built with their father in the backyard of their Krum, Texas home. Caleb won a freestyle bronze medal in his X Games debut in 2010. He won bronze again in 2011. Last year he won best trick silver, finishing behind Colten’s gold.

Caleb won silver in the 2012 best trick contest while recovering from a broken pelvis and a broken tailbone he sustained in a crash during practice the day before the event.

Hours before his Thursday crash, Moore told The Denver Post that his snowmobiling career was launched at the X Games after barely a month of practice.

“Took a bronze medal after 30 days of practice,” Caleb said. “It’s been history from there. It’s been a great ride.”