I've posted about Father Mychal Judge before. He was an FDNY chaplain who died that day.
"That Final Morning
On the morning of Sept. 11, 2001, Judge rushed with some off-duty firemen to the World Trade Center, which had just been hit by the first plane. Tom Von Essen, who was then commissioner of the New York Fire Department, saw him in the North Tower.
"And he looked really concerned," Von Essen recalls. "We didn't talk. We always talked. We always fooled around. But we didn't that morning."
As it happened, French documentary filmmakers were inside the North tower. Their camera captured some of the last moments of Mychal Judge's life. In the film, says his friend, Father Michael Duffy, you can see the priest standing by the plate glass window, watching the bodies fall on the patio outside."
http://www.npr.org/2011/09/05/140154885/memories-of-sept-11s-first-casualty-burn-bright