9/11 Heroism of 'Man in the Red Bandanna' Detailed in New Book by Tom Rinaldi

— -- Throughout his childhood, Welles Crowther carried and wore a red bandanna, and as a Division I athlete playing lacrosse and hockey at Boston College, the bandanna was always there under his helmet.

After graduation, the 24-year-old took a job as an equities trader at Sandler O’Neill and Partners on the 104th floor of the south tower of the World Trade Center. It was Crowther's dream job, but something was missing.

"Welles called me one day. He said, 'You know, Dad, I think I want to change my career. I think I want to be a New York City firefighter,'" Jefferson Crowther recalled.

Welles Crowther had been a volunteer firefighter in Rockland County, N.Y., and when terrorists attacked the twin towers on Sept. 11, 2001, he put that training to work and lost his life while helping others.

Crowther's story is told in the new book "The Red Bandanna: A Life," by ESPN reporter Tom Rinaldi, who appeared on “GMA” today to explain that Crowther had become attached to carrying a red bandanna after receiving one from his father when he was just 6 years old.

After the north tower was struck by a passenger airplane that had been hijacked by terrorists, Crowther called his mother, Alison Crowther, and left a message to let her know he was OK.

But then the south tower -– the one in which Crowther’s office was located -- was struck by another hijacked commercial airliner.

On that same day, terrorists also commandeered airliners that crashed in Shanksville, Pa., and at the Pentagon in Washington, D.C. Nearly 3,000 people were killed that day as a result of the attacks at the three locations.

Multiple survivors of the attack on the south tower describe being helped by a man whose mouth and nose were covered by a red bandanna who set up triage and helped get them to safety.

“You heard this man's voice say, ‘I found the stairs. Follow me,’” Ling Young, one of those survivors, said.

That man -– later identified as Crowther -- reportedly carried one woman on his back down 17 flights of stairs and then went back up for another group of people. It's believed that he helped save as many as 12 lives.

"When I heard the news that the tower had come down, I knew in my heart of hearts that Welles was gone," his mother said. "It was just a mother's heart knowing."

Her son's body was found months later next to the bodies of a group of firefighters. He was posthumously made a member of the New York Fire Department.

Jefferson Crowther said he is amazed by what his son did for others in his final moments.

"To know that Welles in that figurative sense took off the equity trader hat and put it on the table, picked up his helmet -- firefighter's helmet and went to work. For me, that was an incredible, incredible thing to know," he said.