On the morning of 9/11 in New York City, ordinary people picked up video cameras and recorded. One of these people was Cheryl Dunn.

Dunn was filming the chaos in the street outside her Lower Manhattan apartment when a jolt like a “small earthquake” knocked her five feet backward. It was the collapse of the South Tower. When she stood back up, a black wall of smoke and debris came crashing through the apartment windows.

“It was like being underwater,” says Dunn.