Soon after the explosions, there appeared on the website of the Boston Globe a video of the moment. Runners in the city's iconic marathon are jogging across the finish line and everyone is cheering, when there is a clap of thunder and an orange bloom of fire from within a ring of flags honouring the nations represented in the race.
It is followed, seconds later, by another blast from just down the street. The cheers become shrieks, falsetto shrills of panic and fear and the videographer carries you forward, to where the smoke is drifting and police, runners and bystanders rip barricades apart trying to reach the epicentre of chaos.
"We need help!" someone cries.
And the videographer whispers three words to himself. "Oh, my God," he says.
He says it again. "Oh, my God."
He keeps saying it, probably doesn't even hear himself, probably doesn't even realize. "Oh, my God."
On a day that will be filled with expert analysis and speculation, in a moment of keening, lamentation and loss, on an afternoon that will require a presidential expression of empathy and resolve, no one will say any words more fitting, more viscerally descriptive than those. They are an entreaty of the Almighty, yes.
They are also a susurration of helplessness in the face of stark and awesome evil.
Oh, my God because blood sits on the sidewalk in pools.
Oh, my God because pieces of people litter the streets.
Oh, my God because our nightmares now walk in sunshine.
"We can't do this anymore," a man named Allan Kaufman tells a reporter. "We can't have open events anymore. You can't control it." It is a measure of the day's horror that for an instant, his words, spoken in a rawness of anguish, seem to make sense. But they don't, of course. Not really.
Even if what Kaufman suggests were possible -- and it isn't -- it is not something we could choose. The need to gather is fundamental to the human condition, part of what makes us who we are.
So there will always be marathons. There will always be baseball games and Super Bowls. There will always be shopping malls at Christmas. There will always be concerts and movies. There will always be places where people gather to compete, fellowship, laugh, shop, enjoy.
So there will always be opportunities to do to us what somebody did in Boston. "No man is an island," wrote John Donne, "entire of itself. Each is a piece of the continent, a part of the main."
Even in grief, this truth proves itself. On street corners, people with glittering eyes and fallen hearts embrace people they do not know. In hospital waiting rooms, strangers lend one another strength. And in churches, synagogues and mosques, people gather to seek release from lacerating pain or simply to whisper again and again.
Oh, my God, because nearly 180 people were wounded and maimed.
Oh, my God because three people were killed.
Oh, my God, because an eight-year-old boy will never get to finish the chalk drawing of butterflies and flowers he left in the driveway of his home.
Oh, my God, because sometimes, you just run out of words.
But the eight-year-old Martin Richard knew what to say. There is a picture of him circulating online. Taken at school a year ago, it shows a handsome, gap-toothed little boy holding up a sign. "No more hurting people," it says. "Peace."
His death, then, is a bitter irony and visceral reminder that we live fragile lives on a fragile planet. And when you come right down to it, all we really have is each other.
That's our vulnerability -- and greatest strength.
We are wounded now, yes, Oh, my God. But we stand together. We stand defiant. And we stand with Boston.
Leonard Pitts Jr., winner of the 2004 Pulitzer Prize for commentary, is a columnist for the Miami Herald