By: Michael George, CBS Correspondent

New York (CBSLA) – It was one of the most powerful stories of heroism from September 11th, 2001. A group of firefighters somehow survived inside the collapsed World Trade Center for four hours and managed to save a woman’s life.

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Retired FDNY Lt. Matt Komorowski’s keeps the helmet he wore that day in his home. “It reminds me of the firemen that we lost that day. It reminds me of all the lives we lost that day,” he says.

20 years ago, Komorowski and the other members of Ladder Company 6 went into the World Trade Center’s north tower searching for survivors. They tried to climb more than 90 flights of stairs as debris fell around them. “My captain turned to us and say, ‘Firemen will die today.’ And that was a very poignant moment for all of us,” Komorowski says.

When the south tower collapsed, Ladder Company 6 got the order to evacuate. That’s when they spotted Josephine Harris, who needed help getting down the stairs. “We were taking her down, and at about the 8th floor, our building came down,” Komorowski says. The north tower collapsed on top of them. “I immediately screamed to the guys in front of us to move.”

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What happened next almost defies explanation. The entire building around them was destroyed, but part of Stairwell B, where they were assisting Harris, remained standing. “Where she stopped turned out to be the spot we needed to be,” Komorowski says.

They spent four hours trapped in the rubble, but all six men on the crew and Harris made it out alive. “There were so many other firemen that day that were doing exactly what we were doing. Why we survived, we have no idea,” Komorowski says.

Harris, who worked as a bookkeeper for the Port Authority, stayed close with Komorowski and the other firefighters who saved her. “We had a special bond with her, she was our guardian angel,” he says. “If she had continued down to the lobby, and then our building came down, we wouldn’t be around.”

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In 2011, Ladder Company 6 served as pallbearers when Harris passed away, carrying her one last time.