When he walks through the science wing, kids are lying on top of big pieces of construction paper, tracing one another's bodies with black markers. Some lie there giggling; some lie perfectly still, as if bodies at a crime scene. In this moment, the principal smiles uneasily at his kids and steps briskly, wordlessly past, thrown forward into the business of his day, pressing his lips tightly as if holding five years back.

We die many times, says Reverend Don, and experience many different forms of grief. We endure the hatred of others in order to listen, to reach out, to hear the truth, to change one life.

Jail is where Reverend Don now spends his days, working with the inmates at the Adams County Detention Center for $20 an hour. Stand here in his windowless office and there may be room for only one other person. How did he go from a congregation of 1,000 people and a compensation package worth $90,000 a year to this?

Reverend Don isn't shy about telling the story: He got fired, sold his house, slid into a depression, suffering from the aftereffects of Columbine, in an endless loop over Columbine. He moved to Chicago for two years to lead a congregation beset by ills. He's ashamed to say now that he didn't answer a spiritual calling on that occasion; he did it for the money. And then, in Denver, his son had a baby. Reverend Don became a grandfather, and he and his wife decided: Job or no, they were moving back.

Here at the jail, there are 1,200 inmates, some of them the worst of the worst: accused bank robbers and killers and pedophiles. But there's an unusual honesty here, too. You can't really lie about who you are when you're wearing prison pinnies. And if you mean to redeem yourself—both spiritually and personally—well, then, eventually you're going to get around to seeing Reverend Don.

On this day, nearly five years after laying Dylan Klebold to rest, he offers counsel, meets with a handful of inmates to discuss the Bible, conveys information to inmates about sick relatives—and then delivers bad news. Just as he prepares to brave the rush-hour traffic to go home, he's handed a slip of paper. An inmate's aunt has passed away, and it's Reverend Don's charge to break the news.

Reverend Don takes his prisoner, a thin man in on a petty offense, to a private room. He tells him that his aunt is dead, and the man breathes in, once sharply, and then starts hyperventilating. "No, no, no," he keeps repeating. "She was my mother's favorite." The minister asks if his mother's still alive, and the man answers in the negative.

"So you're going to be mourning her death again, aren't you?" he says.

"Yes, I am," the man says, in a small voice. "My mother."

"How many days you got left?"

"Eight."

"Shit. That's bad luck," says Reverend Don. "That's rotten. You won't make the funeral."

"That's right," says the man. And now he seems to dissolve, his eyes welling, his lips moving but making no sound. Reverend Don reaches out and clasps the prisoner's arm gently but with purpose. It's an act of intimacy in a place where knives end up in people for less.

"Hey," he says, "can you look at me?" The prisoner looks up. "I don't know what landed you in prison," says Reverend Don, "but I'm here for you...to talk. Okay? We can talk about anything—your aunt, your mother, the Bible. We can talk about anything."

Reverend Don is gazing upon the man, perhaps even as he did the killers' parents, and only sees his suffering. "You're not alone," he says.

So it's time to return. Come. One last time. Everything is moving so quickly backward, can you feel it? Armies drive in reverse through orange sandstorms half a world away, fallen soldiers take their feet again, the injured suddenly are given back limbs—and all of them are placed on transport planes, flying backward, for home. Upon their return, there's an interlude of national mourning, jingoistic rage and confusion, and then, on the southern tip of Manhattan, two jets are miraculously belched whole from inside skyscrapers and rematerialize at 30,000 feet. On the streets, no one bothers to look up. Soon the passengers are walking backward down the gangplanks in Boston, returning home to their families. The skyscrapers empty of people, too, who then return to their families. The public consciousness turns to money, the millions made with every upward burble of the market. And it just keeps going up.

As complicated as this country is, America, on the morning of April 20, 1999—on Zero Day—is a much simpler place than the one it will become that afternoon. There's a girl on the lawn eating her lunch in front of Columbine High School. There's a boy stepping outside with his buddies for a cigarette. And there's another, up in the library, finishing his statistics homework, smiling at the memory of his last-ever basketball game, the fluid up-and-downs on the court, the shot at the buzzer.

Can you feel where this is taking us? Time keeps moving backward. The teenagers are becoming children again, as they've always been. A boy named Brooks poses in a picture with his friend Dylan, dressed in Cub Scout uniforms. Now they're running backward out the doors of the elementary school, their feet in funny kicks, to their mothers in waiting station wagons. The children pull apples from their mouths, place them whole on the table and shed their clothes for warm pajamas. Even as their mothers wake them, they fall back to sleep. Long, unbroken hours of sleep during which their hands grow smaller.

Only someone like God could tell us what they dream now, sleeping as they do. But sometime during this night, God temporarily goes missing. A primal force moves the stars. Snowflakes fall like locusts, banishing the earth. Somewhere, in this night, an errant seed lights down. A silver hook fastens. These are not supernatural acts. This is real.

Now let the terrible glare of time begin forward again. It's dizzying, this speed. Can you feel it? The babies become teenagers. The guns are bought and hidden in the closet, waiting. The road is cold and silver, swerving all these years later to Columbine High School, where, in blinding sun on a seventy-in-April day, with laughter floating from the cafeteria, two boys cross the parking lot.

Two boys are crossing the parking lot now—crossing again...and again. And for the last time: These killers are crossing the parking lot again. No one stops them. No one even sees them. What comes next is irreversible: We are eating lunch on the lawn, going for a smoke, finishing our homework.

Listen: There's innocent laughter—and then, in a second, there's none at all.

Michael Paterniti is a GQ writer- at-large.