so i grabbed one of my staff guys, emt rich zarrillo, and i said, rich, go to pete ganci.on't talk to anyone else, and deliver this message. the buildings are in danger of collapse. >> in this four-second video, at far left you see rich zarrillo's blue shirt. he's delivering the warning to pete ganci. zarrillo hardly got the words out when ganci's attention was drawn to a roar from the south tower above him. >> loud noise. had no idea what it was. all we saw was a plume of dust and smoke and debris. >> in the moment before, melissa doi had given the 911 operator her mother's phone number and the message that her daughter loved her. then there was silence. >> oh, my god. are you all right? you're going to be fine. you're going talk to your mother yourself. you've got to think positive. you've got to stay calm. you're going to talk to your mother yourself, all right? melissa? >> palmer's last radio transmission was battalion 7 to ladder 15, and there is nothing after that. that's when the tower collapses. >> he must have known that with every step he ascended, his chance of