On the morning of September 11, 2001, I was working at a small UPS delivery center a few blocks from the World Trade Center. At the sound of the first explosion, we ran outside and stared at the burning North Tower. We were in a state of shock, which then turned to panic after another plane crashed into the South Tower.

We rushed back into the center to grab our things and get home — until we were stopped cold by a supervisor I’ll call Billy, who said we were to stay where we were until he heard otherwise from his bosses.

In this moment, all of us worried that another plane, maybe more than one, might come crashing in at any moment — or maybe something even worse that we hadn’t seen yet. Even as Billy spoke, we could see hundreds of people streaming uptown through the glass walls of our delivery center. A friend of mine who I’ll call Jason started moving toward the door.

“If you leave,” Billy said, “turn over your ID, because you’re not coming back.”

What followed was maybe forty-five seconds of pandemonium — Billy yelling at Jason, me yelling at Billy, others rushing to Jason to keep him from attacking Billy — that ended when a few of us made a simple decision: we were going to walk out. The other twenty or so workers in our center quickly followed, and our brown uniforms dissolved into the mass of blue and black suits fleeing the Financial District.