ganci sent sal cassano to set up a new command post. 28 minutes later, cassano was on his way back. >and then i look up and all i could see was the antenna from the north tower imploding. >> get out of the tower! it just collapsed! major collapse! major collapse! major collapse. >> i, in my mind, had to be resolved with death. >> regina wilson was on the street below the tower. she was with engine 219 in her second year as a firefighter. >> and i prayed, and then i just asked god to just protect me and, if he couldn't, i knew that i would die doing what i love. >> inside the collapsing north tower, the men of engine 39 were caught in a stairwell. >> and it started out slow, boom, boom, boom. then it got quicker. pretty soon, bam, bam, bam, bam coming down. >> jeff coniglio and jamie efthimiades were on the stairs near the ground floor with 110 floors above them. >> it took ten seconds for it to come down. but it felt like ten minutes. i saw i was in the background of a funeral. i saw my casket. i saw my parents, my wife sitting in the front, and as i'm watching this, i'm like, all rig