BMX legend Dave Mirra was found dead of an apparent suicide on Thursday, and celebs and sports stars took to social media to remember the 41-year-old sports icon.

"Goodbye Dave Mirra, a true pioneer, icon and legend," wrote skateboarder Tony Hawk, who is tied with Mirra and Joe Parsons as the fastest athletes to win 14 medals at ESPN's X Games. "Thank you for the memories... we are heartbroken."

WATCH: Dave Mirra, BMX Star and Former Host of MTV's 'The Challenge,' Found Dead of Apparent Suicide

“I'm in complete shock,” wrote motocross star Carey Hart on Twitter. “Angry, heart broken and just sad at the passing of my friend Dave. Heart broken 4 his daughters and wife. #DaveMirra.”

“Rest in Peace Dave Mirra,” tweeted fellow BMX rider Brian Kachinsky. “Thank you for pushing the boundaries of what was possible. You are a legend.”

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Mirra also hosted MTV’s The Challenge for two seasons from 2004-05, and co-host Mark Long opened up about the BMX rider’s death in a statement to ET.

"Dave was an early fixture on the MTV Challenge franchise,” Long said. “He was one of the first extreme sports figures to make the jump from competing to hosting. He was a mild mannered man on set that always seemed to be focused on doing a great job. He will be dearly missed within the MTV family."

"My thoughts and prayers are with the family of Dave," Challenge alum Kenny Santucci said in a statement to ET. "His courage and passion in everything he did will always be remembered. May he rest in peace."

"Dave Mirra lived his life doing the impossible, and that's how I will always remember him,” added franchise vet Camila Nakagawa, who didn’t participate in either of Mirra’s seasons. “RIP to a true legend and pioneer."

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Other celebs expressed their disbelief at Mirra’s death on Twitter.

WATCH: BMX Icon and 'The Challenge' Host Dave Mirra Dead at 41