By Devon O’Neil, ESPN

Chelone Miller, the younger brother of Olympic champion ski racer Bode Miller and a professional snowboarder who excelled in three disciplines, was found dead Sunday in his adopted hometown of Mammoth Lakes. He was 29.

A close friend discovered Miller unresponsive in the van in which Miller lived, outside his friend’s home, and the friend alerted authorities at 12:45pm.

According to the Mono County Sheriff’s Office, which confirmed Miller’s death on Monday, the cause of death is unknown pending an autopsy. Foul play is not suspected. Miller had a history of seizures since being badly injured in a 2005 motorcycle crash that left him in a coma for 11 days. Miller was well-known in Mammoth Lakes for his versatile riding talent, free spirit and fearless approach to big mountains. He was one of the few pros who could hit big jumps, ride precipitous natural terrain, and compete with the best snowboardcross racers in the world.

Snowboarder Chelone Miller died from an apparent seizure. Photo/Ski Channel

According to friends in Mammoth Lakes, Miller — affectionately known as “Chilly” — played golf Friday and spent Saturday lapping the resort’s terrain park. He had planned to fly to Alaska to compete in the Arctic Man race on Friday, an event that pairs snowmobilers with skiers and snowboarders who reach speeds in excess of 80 mph. “He was a very talented snowboarder and a great friend,” said John Teller, a Mammoth-based skicross racer who won X Games gold in 2011.

“Chilly always struck me as one to do things his way,” added Nate Holland of Squaw Valley, a seven-time X Games gold medalist who competed against Miller in snowboardcross. “He’d pop up here and there in his van as kind of a lone wolf, and throw down. He was a hard-charging snowboarder.”

Holland spoke from Alaska, where he was expecting to see Miller for the Arctic Man. Last year, Holland said, Miller suffered a seizure on the day of the event and was airlifted to a hospital. After stabilizing, Miller returned to the course and raced.

“I remember the organizer saying, ‘If Chilly says he’s racing, he’s racing, and we’re not going to finish this race until he gets back from the hospital,'” Holland recalled.

Most recently, Miller had taken steps to qualify for the 2014 Olympics in snowboardcross. He finished fourth at last month’s national championship in Utah, ahead of Holland and two-time Olympic gold medalist Seth Wescott. Miller also won the overall championship on the 2013 Rahlves Banzai Tour, clinching the title with a win at Sugar Bowl last month.

Born on the family’s land in Easton, N.H., in August 1983, Chelone was one of four Miller children who grew up without running water or electricity. They used kerosene lanterns for light.

“It was pretty much old-school livin’,” he said in a 2010 Snowboarder magazine interview. “I’m glad I had the opportunity to grow up that way.”

Miller suffered a traumatic brain injury in the 2005 dirt-bike crash near his hometown and later said he lost his memory for an entire month. After recovering, he suffered his first seizure while riding a chairlift at Mammoth Mountain and fell 25 feet, landing on his back.

Miller finished 28th in Snowboarder X in his only X Games appearance in 2010. He also was an alternate for Slopestyle that year.