Josephine Harris was a widow and grandmother from Brooklyn. She worked as a bookkeeper for the Port Authority of New York and New Jersey.

The morning of September 11, 2001, Harris was in her office on the 73rd Floor of the North Tower. When American Airlines Flight 11 hit the building, Harris and her coworkers began evacuating.

But Harris, who was recovering from a recent accident, soon began struggling on the stairs. Needing to rest frequently, she made it down more than 50 floors (various accounts of that morning say she was somewhere between the 15th and 20th floors) when her legs just started to give out.

Sad and distressed, Harris believed she couldn't continue.

Meanwhile, firefighters from FDNY Ladder 6 were somewhere around the 27th floor when the South Tower collapsed. Knowing their time was limited, six members of Ladder 6 began making their way out.

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That's when they ran into Josephine Harris.

Harris didn't want to slow down their evacuation, but the firefighters weren't going to leave Harris behind. Firefighter Billy Butler told The Guardian in October 2001, "We started down with her and it was a slow process because she was extremely fatigued, her legs were collapsing."

Captain Jay Jonas knew the clock was ticking. Together, the six members of Ladder 6 took the stairs at Harris's pace.

They made it to the fourth floor when the North Tower collapsed around them.

"I have never been in a tornado or an earthquake," said Butler, "but I think it was like a combination of both. You could see stuff coming down past your face and the next minute it was going up past your face."

It took a few moments, but soon Ladder 6 realized they and Josephine weren't the only survivors. Chief Rich Picciotta of another company, an Engine 16 lieutenant, a Port Authority police officer, and three or four firefighters from Engine 39 were with them, too.

At first, the group had no idea how bad the damage was.

"We didn't give a Mayday initially because we thought we could walk out of there like gentlemen," Butler said. "Captain Jonas told them that they were in the north tower's stairway B. The reply came back, 'Where's the North Tower?'"

Butler used a cell phone to call his wife, and she relayed a message to his firehouse with their location. They were found alive under more than 100 floors of rubble.

Thanks to Josephine Harris.

Many of the people who had passed them on the staircase, as well as those above them, did not survive the North Tower collapse.

In the 9/11 Memorial & Museum, there's a picture of Harris holding a jacket with the Ladder 6 emblem and "Josephine | Our Guardian Angel" embroidered on it.

"Where she stopped turned out to be the spot we needed to be," said retired FDNY Lt. Matt Komorowski. "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."

Harris would later recall that morning. “All I wanted to do was get to the lobby," she said. "I had no idea it wasn’t there.” She remained close with the firefighters of Ladder 6.

Josephine Harris passed away in 2011. Members of Ladder 6 served as her pallbearers.