Exactly 10 years after the first plane hit, New York City police officer Danny Shea, a veteran of the Afghanistan war, snapped a salute at the corner of the reflecting pool that stands on the footprint of what was the North Tower. Just as he was a decade ago, photojournalist David Handschuh was there to share the moment with the world.

Handschuh was struck by the angular geometry of the scene, with the flag-draped One World Trade Center rising in the background. It summed up the sense of grief, solemnity and renewal that infused the event...