I told her that one of the towers was falling and that she should follow me out. We ran to the lobby where people were waiting for the elevators. A co-worker grabbed me. “Let’s take the stairs.”

We raced down a flight of stairs, merging into people coming down from higher floors. We emerged into the building lobby. Just as I turned to face the glass doors and windows facing Maiden Lane, I saw the sky change from beautiful, bright daylight to complete darkness. It was as if someone had taken a giant, charcoal-gray blanket and draped it over the entire building, pressing it tightly against the glass.

I stood there completely stunned. After a few seconds, the revolving door began to turn and a single man entered, covered from head to foot with concrete dust. For a second, it seemed he had just walked in from a blizzard—only this blizzard was comprised entirely of dust.

A few minutes later, the door began to revolve again. In came an older black woman, who like the man before her, was completely covered in dust. I took a bottle of water from the store in the lobby and gave it to her.

The building guards began directing us toward the parking garage. More than one hundred of us had entered the garage when the dust became too thick to breathe. Somehow my co-worker and I became separated. People in the garage began to yell to those trying to exit the lobby and, slowly, we all re-entered the lobby. I found her again and it’s safe to say we were relieved to find each other. We were directed toward the back of the building, the side that faces away from the direction from which the dust was coming.