On Sept. 11, 2001, four commercial planes were hijacked by terrorists. One plane crashed into the north tower of the World Trade Center in New York City, another went into the south tower.
In Virginia, the Pentagon building was also hit by a hijacked plane, and the fourth crashed in a field in Pennsylvania, after passengers fought back and caused the plane to miss its intended target, the U.S. Capitol.
The dreadful attacks sent shock and horror through the nation and the world. The attacks claimed the lives of thousands.
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There are very few survivor accounts, but many of those who did survive the horrific events of that day have shared their stories. One of those stories has become known as "the miracle of Stairwell B."
At 8:46 a.m., a hijacked plane slammed into the north tower of the World Trade Center, prompting a rush of emergency personnel to the scene. Shortly after, at 9:03 a.m., a hijacked plane flew into the south tower.
The south tower was the first to collapse at 9:59 a.m., followed by the north tower at 10:28 a.m. Very few people survived the collapse of the towers, but a group of emergency personnel and one civilian did survive – with each other's help.
When the south tower collapsed, a group of firefighters and one police officer were still inside the north tower. This group included David Lim, a Port Authority K-9 officer; Capt. John "Jay" Jonas, FDNY's chief from Ladder Co. 6; Firefighter Bill Butler; Firefighter Sal D'Agostino; Firefighter Matt Komorowski; and Battalion Chief Richard Picciotto.
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With the collapse of the south tower, they were ordered to evacuate and began to make their descent down stairwell B.
When they reached the 22nd floor, the firefighters from Ladder Co. 6 found a distraught woman named Josephine Harris, who was a bookkeeper for the Port Authority. She was exhausted and could not move on her own due to an injured leg. The firefighters took Harris with them for the remainder of their descent and carried her down the building.
At 10:28 a.m., the group started hearing a rumble as they walked down stairway B of the north tower.
Miraculously, the 12 firefighters and one officer, along with Harris, all survived the collapse as they were tucked away in stairway B, a staircase at the center of the building's core.
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How the group survived the collapse is still somewhat of a mystery. That stairwell seemed to provide protection for the survivors.
"The tower came down like a peeling banana, and it peeled around us," Jonas told USA Today.
All 14 survivors in the stairwell not only escaped the north tower ruins, they also had no life-threatening injuries.
The firefighters that were with Harris have described her as their "guardian angel."
"We had a special bond with her. She was our guardian angel. If she had continued down to the lobby and then our building came down, we wouldn't be around," Komorowski said in an interview with CBS News.
The firefighters and Harris remained close in the years after 9/11 until her death in 2011.
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During her funeral, the firefighters of Ladder Co. 6 were her pallbearers.
Today, Stairwell B is on display at the National 9/11 Memorial & Museum in New York City.