i'm bryant gumbel.understand there has been a plane crash on the southern tip of manhattan. >> reporter: 20 years ago this week -- >> oh my god, another plane has just hit another building. >> reporter: after the worst terror attack in american history, the best of america rushed in to help. >> and that's what the guys are taught. >> reporter: joe and chuck downey knew their father, ray downey, would be among them. did a part you have hope maybe there was a chance your father wasn't there in the mix? >> i thought that. >> yeah. i said even if he was home, he would have been heading in. >> he would have been there no matter what. >> reporter: sure enough, a film crew happened to capture deputy chief downey that morning, coordinating rescues in the lobby of the north tower. raymond matthew downey sr. knew the dangers that day perhaps better than anyone. >> hello, my name is ray downey senior. >> reporter: he developed trainings in technical rescue, meaning he was an expert in pulling people from collapsed