Against a gray expanse of pavement, a man in a neon orange jersey sprawls on his back, his gray hair wild from the force of the explosion that has knocked him to the ground. His gaze is turned toward three police officers in yellow vests who have unholstered their guns and walkie-talkies and who sprint through smoke and haze.

By now you have seen this photograph a dozen times, one of hundreds of visual artifacts for a tragedy that played out in a horrifyingly visual manner — on screens, through footage, in pictures.The Boston Globe posted it last Monday afternoon, and by that evening it had been retweeted 2,300 times. The runner was identified: Bill Iffrig, 78, a grandfather and retired mason from Lake Stevens, Wash., who later told CNN how the shock waves had made his legs “jitter.”

His identity almost didn’t matter. He was simply the Fallen Runner.

A week after the Boston Marathon bombing, we are collectively composing the first draft of history. We curate the images that will come to represent this week: A pair of grainy stills from a department store surveillance camera. Newsreel of police officers, swarming a Boston suburb in the middle of the night. Newsreel of police officers, cheered by the city. Endless online galleries prefaced with, “Warning: Graphic.”

We do this again and again — during wars, after assassinations. Chaos is organized into pixels, frenzy is made still and two­dimensional. We catalogue and remember.