Police officers warned people in the vicinity to move north, that the buildings could fall, but most people found that unthinkable. They stayed put or gravitated closer.
Abruptly, there was an ear-splitting noise. The south tower shook, seemed to list in one direction and them began to come down, imploding upon itself.
"It looked like a demolition," said Andy Pollock.
"It started exploding," said Ross Milanytch, 57, who works at nearby Chase Manhattan Bank. "It was about the 70th floor. And each second another floor exploded out for about eight floors, before the cloud obscured it all."
Seth Bower was on Broadway when the force of the collapse knocked him over onto other people. Bodies fell on top of him -- not all of them, he thought, alive.
A plume of smoke reminiscent of an atomic bomb rose upward and then descended to street level and sped uptown. People began running, chased by the smoke. The air rained white ash and plaster dust, coating people until they looked ghostlike.
Some people were screaming, and many were in shock. "Don't breathe the air," people shouted. "It could be toxic." People held their breath or covered their faces as best they could with cloths or their shirts.
Michael Clinch, a security officer for an Internet company, left his office soon after the first plane struck and was standing on Broadway talking to a police officer when the first tower fell. He saw a woman running, grabbed her and pulled her under a sport utility vehicle with him. "We got under the truck and waited until it got light again," he said. "There were cars just blowing up. They were trying to get equipment off this emergency truck and get it into a building and all these cars just blew up. One would blow up and set off the next one. It got so bad we just couldn't do anything any more and we had to get out of there."
Ten or so blocks north of the towers, the smoke had been outrun and it began to dissipate into the air. People stopped, turned and looked downtown. As the air cleared, an unthinkable site presented itself: empty space where a 110-story tower had been.
--U.S. ATTACKED; HIJACKED JETS DESTROY TWIN TOWERS AND HIT PENTAGON IN DAY OF TERROR The New York Times September 12, 2001