Trail ultrarunner Dave Mackey suffered severe leg injuries after a fall from a ridge near the summit of Bear Peak in Boulder, Colorado, on Saturday morning. He was evacuated by members of the Rocky Mountain Rescue Group and is recovering in stable condition.

Mackey, a three-time U.S. Ultrarunner of the Year and former Rim to Rim to Rim record holder, was coming down a route on the west side of Bear Peak when he stepped on a rock—one he had stepped on hundreds of times, he later told Competitor.com—and it gave way. He reached out for another rock as he was falling, but that gave way as well. After he fell 20 feet over stones and branches, a boulder weighing between 300 and 400 pounds landed on his leg, the tibia and fibula bones of which were already broken.

Mackey called for help. Other runners and hikers kept him warm, called 911, and levered the boulder off with a large stick, according to 9News. Fellow Boulder trail runner and climber Bill Wright helped stabilize Mackey before the Rocky Mountain Rescue Group arrived. “If there is a tougher, more badass dude than Dave Mackey, well, I don’t believe that,” he told Competitor. “His ability to stay calm, endure intense pain, and handle a horrific injury was inspiring, astounding, and had everyone involved shaking their heads.”

Over four and a half hours, Rocky Mountain Rescue volunteers were able to stabilize Mackey and belay him down to a wheeled litter. They then took him down a trail to a waiting ambulance. At the hospital, Mackey underwent surgery to repair his left leg. He now has a metal rod, plates, and screws in his leg and will need further operations to heal the soft tissue and clean the wound.

“If anyone can come back from this, it’s Dave,” Wright told Competitor, “and I’m sure he will, but I suspect that it is going to be a while before he’ll be once again beating us all at everything.”