Looking back over his nearly 30 years as a highly decorated first responder in Colorado's Roaring Fork Valley, Michael Ferrara has trouble pinpointing the exact moment when his life began to unravel. His ordeal arrived not all at once but in a long spool of assaults on his soul and psyche. A plausible starting point, though, might be March 29, 2001, and a nightmare that occurred at the airport in Aspen.

One fine warm day this past August, Ferrara and I decided to walk over to the site. His six-year-old mountain-rescue dog, a German shepherd named Lhotse, led the way. Ferrara wore sweats and trail-running shoes. His skin was ruddy from the sun, his graying strawberry-blond hair cropped short. We stopped outside the Aspen airport's fence, which is designed, among other things, to keep herds of elk off the tarmac. Ferrara squinted through the sun as a Learjet taxied and then shot into the sky.

"I'm OK with this," he assured me. "I've learned to recount without reliving—it's part of the therapy."

The weather was snowy and cold on that evening nearly ten years ago. One minute past seven o'clock, a Gulfstream III came in on an instrument approach. Fifteen friends from Los Angeles, most of them in their late twenties, had chartered the jet for a few days of spring skiing to celebrate a buddy's birthday. Something went wrong on the final descent. The pilot apparently couldn't see the runway. A wing tip caught the ground, the plane flipped, and the tail segment broke off. Then the plane exploded into flames.

Ferrara, who at the time was both a Pitkin County sheriff's deputy and an assistant coroner, was among the first to arrive. Over the years, he had worked on a half-dozen small-engine-plane crashes in the mountains around Aspen. In other jobs as a paramedic, ski patroller, high-angle rescuer, and avalanche specialist, he'd often dealt with blood and trauma and heartache. Among scores of incidents, he was first on the scene when the late senator Robert Kenned...