Then I ran into the same policeman who’d been yelling at me before, and I was escorted out. The area was flooded with police trying to funnel all the civilians uptown. I figured I’d turn onto Vesey and go a few blocks east before heading downtown and then doubling back. I didn’t make it very far. There was a roar that sounded like being next to a jet engine, which I first took for another crashing plane. I was wrong: WTC 2 was collapsing, around 10 a.m. People started to stampede. I joined them. The cloud rolled out toward us; we were actually racing it up Park Row, heavy, suffocating dust, grains of something hard. It caught me finally. I tried to hold my breath and find a doorway while I could still see.

Somebody opened the door to a Starbucks. About twenty people were inside. The manager told us all to drink water and handed out bottles, telling us to take juice instead if we wanted it. The windows turned opaque and we heard things bouncing off the glass. The manager told us all to get into the basement. “Does anybody need anything? Is everybody all right here?” he asked. We crowded into the basement. A woman in a Starbucks apron was sobbing uncontrollably; someone she knew named Aaron worked at the towers. The phone rang. The manager answered. “Hello, Starbucks Coffee.”

I walked back down Park Row. I was talking to a policeman at the Broadway intersection at 10:27 when WTC 1 came down. I heard the roar and saw the cloud swell out again. This one carried more debris. We watched it get dark again, then sprinted back to Starbucks. The front window shattered and the store filled with dust. We retreated to an upstairs bathroom and flushed out our eyes and nostrils.

Half an hour later the sun was still barely visible. People were moving in twos and threes toward the river; we were shadows, soundless. I passed bubbling fountains, phones dangling on their cords. A man in a bandanna and sunglasses was photographing an abandoned stand of dusty bananas and plums and nectarines.

What is chaos?

WTC 2 blown to bits, ripped apart. An eggshell-thin frame above a mass of rubble covering most of a city block. Steel girders three feet thick obscenely contorted.

FDNY, NYPD, ATF, Customs, Secret Service, EMTs, Parks Department, men in camouflage, canine units. Smashed and upended trucks, engines, ambulances, police cruisers. Sirens, more machinery. A crushed Mercedes-Benz convertible in flames. Reams of documents layered evenly over everything.

I took a photograph for four men who wanted WTC 2 as a backdrop. Everybody was doing it. Kodak disposables were popular. I saw a piece of somebody’s leg get wrapped in burlap and left beneath a defoliated tree. This had been the staging area for the first response team. It was annihilated when WTC 2 collapsed. Many of the men who had arrived within minutes of the first explosion were missing, buried sixty feet down. Rescue 1 and 2 were gone. Nobody could find the EMTs who had been first on the scene. The 279 Company’s truck was relatively intact but 279 Company was missing.

When a team formed to clear one of the adjacent World Financial Center buildings, I followed. The massive dome of the foyer was intact; the marble floor was slick under the ash. The windows on the west were blackened; those on the east were blown out. I explored the second floor. Reception: phones off the hook, milkshake on desk, computer monitor on floor. Vase of flowers upright and intact. Gym: rows of treadmills and stairMasters, heavy bag, dumbbells, all uniformly beige with dust. It looked too perfect, an artist’s project, life-size in paper mache.

Nicholas Spangler is a staff writer at Newsday.