A weekend BASE jumping accident in a Utah canyon killed two people, one of them a daredevil athlete best known for performing onstage with Madonna at the 2012 Super Bowl, authorities said.

Emergency responders were dispatched Sunday to a report of people injured in a BASE jumping attempt at Mineral Bottom, a remote desert area near the Utah-Colorado line, according to the sheriff's office in Grand County, Utah.

The office confirmed one of the dead was Andy Lewis, an extreme athlete known for feats in BASE jumping, a dangerous sport that involves parachuting to the ground after jumping from a tall fixed object such as a building, bridge or desert cliff overlooking a deep canyon.

The victims had been conducting a tandem jump in which two people are harnessed together, according to a social media post by Aerial Arts Moab, an acrobatics company that described Lewis as "co-owner and best friend."

Lewis also owned BASE Jump Moab, a business that offered tandem jumps to inexperienced customers who would be harnessed to a guide wearing the parachute. Promotional videos on the company's website show pairs of people stepping off the edges of towering cliffs and briefly plummeting before their parachutes open.

Lewis' risk-taking knew few bounds  

In BASE jumping circles, Lewis had a huge following and a reputation for pushing the envelope - leaping into tighter spaces or deploying his parachute later than his peers would dare, said John McEvoy, a BASE jumping instructor in Twin Falls, Idaho, who has jumped with Lewis.

"He had an incredible level of athleticism and skill that was developed over years of practice," McEvoy said. "But then he would take an incredible amount of risk."

Grand County Sheriff Jamison Wiggins confirmed the other person who was killed was Danny Joe Kregle, a 68-year-old father and grandfather who was described by a family member as an accomplished businessman.

"Danny had a wonderful sense of humor and was always looking for ways to make people laugh," relative Sydney Laverty told The Times-Independent. "One of his greatest joys was performing magic tricks alongside his granddaughter."

Lewis was also a prominent figure in the niche sports of slacklining and tricklining, which combine elements of high-wire walking with aerial acrobatics - sometimes at perilous heights.

He went from obscure athlete to overnight celebrity when he appeared onstage in Madonna's 2012 Super Bowl halftime show. Dressed in a Roman toga, Lewis bounced and executed tricks on his inch-wide line like it was a trampoline while Madonna sang behind him.

"My phone actually rang itself to death three days in a row," Lewis said soon afterward in an appearance on Conan O'Brien's late night show.

BASE jumping much riskier than skydiving, study shows

Though there's no official tally of BASE jumping deaths, a list compiled by the website BASEaddict.com shows 540 total fatalities worldwide since 1981 - including 30 people killed last year. Prominent deaths include BASE jumper Dean Potter and his climbing partner, Graham Hunt, who were killed in 2015 while attempting a wingsuit flight in California's Yosemite National Park.

A study focused on BASE jumping in Norway, published in a medical journal in 2007, estimated that BASE jumping carried risks of injury or death five to eight times greater than skydiving.

Lewis openly acknowledged the sport's inherent danger.

"It's weird to think about how many people are dead, because it's like a normal thing," Lewis told documentary filmmaker Ella Warnick in an interview published last year.

Tandem BASE jumping carries additional risk because it straps together two people, one of whom generally lacks experience, under a single parachute, McEvoy said. But because they involve novices, they also tend to be the most low-risk, basic types of jumps.

"Within BASE, it's a very controversial topic," McEvoy said. "There's a lot of people who say it's the stupidest thing in the world and others arguing: `No, we're giving people the experience of their lives.'"

No one immediately returned phone, text and Facebook messages left Monday for BASE Jump Moab.

Lewis won four straight world championships in competitive slacklining from 2008 through 2011. Lewis set a Guinness World Record for slackline surfing, swaying his feet side to side in a rocking motion that mimics surfing, while keeping his balance above China's Diaoshuilou waterfall in 2011.

In 2014, he walked a slackline suspended between two hot air balloons more than 4,000 feet above the Nevada desert.

Lewis' other sport made him an overnight celebrity, thanks to Madonna.