Jeff Bauman's life changed forever when the bombs went off at the Boston Marathon. What was at first a singular tragedy — the finish line, the man in the cowboy hat, the photo, the legs amputated, the wheelchair for the rest of his life — quickly became the double-sided story of a 27-year-old Costco deli guy turned terror-hunting hero, when we found out Bauman had given investigators some of the clearest information that led to the Tsarnaev brothers.

GQ just posted an exhaustively reported recreation of marathon day written by Sean Flynn from their June issue, which is currently on stands. In it, Flynn tracks people's experiences from the morning of April 15 to its end, in  on of the most emotional, most complete written portraits of that day so far from the victims and the onlookers, all in one place. Bauman's story, of course, was fairly well known: That picture of him was one of the first to emerge on the wires, and the cowboy hat and the wheelchair quickly became an early beacon of the "Boston Strong" movement, especially after an early profile in The New York Times and a quick recovery at Boston Medical Center. Bauman became an even bigger part of the larger narrative when, as first reported by Bloomberg News on the night the suspects were first ID'd by the FBI, it turned out he'd helped investigators positively ID Tamerlan and Dzhokhar Tsarnaev.

But Flynn's story paints in detail what went through Bauman's mind as he witnessed the suspects lurking that day — and that backpack left alone on the sidewalk:

Bauman sees a black backpack on the sidewalk. It occurs to him that at the airport a disembodied voice is forever telling people to be aware of unattended packages. He thinks he should tell a cop about this particular unattended package.

The day went on, disastrously, and permanently changed his life and so many others:

Then he's on the ground, a haze of smoke above him. He hears screaming, dull through his blown-out ears. He can see Michele in front of him. She's down, too, near the fence. Her leg is bleeding, and he can see the white of a bone in her lower leg where the flesh has been torn away. Oooo, Bauman thinks. That's not good.

Nothing hurts. He tries to prop himself up, but he can't. Then he sees his own legs. His feet aren't there. His ankles, parts of his shins, gone. His legs end short in shreds of flesh and jagged bones.

He's hemorrhaging, and his clothes are smoldering, burning into his back, his sides, his right arm. He reaches for his cell phone, thinks he should call someone, but he can't find it.

He believes he is going to die.

Of course, thankfully, that never happened. He's still recovering — the magazine has a nice photo of Bauman sitting in a wheelchair, with very visible scars, but clearly on the right path to get some semblance of his old life back. Read the entire GQ piece here