My cell phone clock read 8:44. Already four minutes late, I started to get angry at having to wait for others to join us before we could go up.

A man and a woman in corporate attire crossed the lobby and approached the elevator. I noticed that the woman had a small rose tattoo above the ankle. As she stepped in, I could see it faintly through her gray stockings, like a coin at the bottom of a pool.

Just as the doors began to close, the building shook as if it were a tackling dummy rammed by a lineman. The elevator car bobbed up and down just an inch or so and then stalled, its doors gaping open most of the way. There was a hollow, far-off sounding thud, like distant thunder, but other than that there was hardly any noise at all.

My mind raced with the possibilities. Having lived through a number of earthquakes in Southern California, I knew that it was not that: The impact clearly felt like it had come from above, not below. Recalling what had happened at the World Trade Center in 1993, the best I could figure was that a bomb had gone off.

Suddenly, I heard a tinny, far-off shriek, like a car being torn in two. Yellow-gray smoke began to seep into the lobby. A piece of concrete exploded against the ground. Then pieces were exploding on the floor all around me, some as small as fists and others as big as garbage can lids.

The people in the lobby scattered like shrapnel from a grenade and broke for the various exits. Aside from a few isolated shouts and screams, I heard no one. Maybe people didn't have time to scream; or maybe they were screaming and I just blocked it out. I felt acutely focused and hyper-aware, totally in the moment, fueled by adrenaline or fear—or a potent cocktail of the two.

Near the lobby entrance, a few men in suits struggled to squeeze back out through the turnstiles. They looked like rats trying to squeeze through holes in a wall. Other people were fleeing the lobby however they could. I didn't know the building very well, having only been there twice. I saw a passage that looked like it led out, so I hurried toward it, and got onto what appeared to be an elevated passageway or deck that circumscribed the lobby. I searched for a way that might lead me out of the building, but it was a dead end.

Through the glass, the plaza outside was eerily vacant. There was no one in sight, yet the ground was littered with personal belongings: handbags and broken eyeglasses, small sparkling items that must have been earrings and watches; a briefcase that sat cracked open and empty, like a shelled oyster. More than anything else, there were shoes—dozens and dozens of pumps and loafers and sandals and high-heels. I knew all these items must have belonged to people, people who were now nowhere to be seen, and I froze up.

I don't know how long I stood there, but it felt like forever. I couldn't stop looking at those shoes. It would have been less chilling if there had been screams or people or some sort of noise, but there was nothing. It was as if a vacuum had sucked everyone and everything away with it, including my thoughts and instincts and decision-making skills.

As I stood there like a statue, a chunk of something landed on the ground outside. I knew it wasn't concrete or glass or steel, because it gave somewhat when it hit. It was charred and misshapen and unrecognizable. For some reason, it looked to me like an overripe eggplant.

I turned and made my way back toward the elevators. There were a few people still in the lobby, mostly crouched in corners and against walls. Through the gauzy smoke, I could see that the turnstiles had been knocked over. I was not sure how—whether by people, by falling concrete or what­­but the way out was now clear.

[On 9/11, the author was a reporter for Waters magazine in Soho, which was hosting a conference that day at Windows on the World on the 106th floor of the North Tower. Delayed because he missed the stop at Cortlandt Street, he was the only one of seventeen staff members to make it out. Eds.]