Americans will mark the anniversary of the September 11th, 2001 terrorist attacks in many ways. Some will attend church services. Others will take part in marches and memorial events. But a few will mark the anniversary in more personal ways.
At 9:43 a.m. -- nearly one hour after the first plane slammed into the World Trade Center -- American Airlines flight 77 crashed into the west side of the Pentagon.
Pentagon security officer John Yates recalls the exact moment of impact. "I remember that there was a ball of flame came from behind me and from my left over my head and I remember being blown through the air and that the room went instantaneously black."
Yates was one of the lucky ones.
"I suffered second and third degree burns over 38 percent of my body from my head my back my face and neck. I had third degree burns on my hands and both my arms that required three grafting operations."
For others, the memory is etched in different ways.
"It's burned into my memory," says Major William Stout, a police lieutenant on the Pentagon's anti-terrorism division. He remembers a scene of utter chaos -- like something from a terrible movie.
"We had a hole in the side of the building. We had people scrambling around everywhere."
"We were picking up plane parts for several days."
But five years after fire rained from the sky, Tom Heidenberger says the anniversary is yet another reminder of what he lost.
"Unfortunately when you think of anniversaries you think of them as a wedding anniversary, or anniversary of a graduation or this, that, and the other. This is an anniversary where I mark the death of my wife."
Heidenberger's wife, Michele, was one of the flight attendants aboard the ill-fated Boeing 757 that was carrying 64 passengers. Heidenberger remembers with some irony, his last words to his wife. He told her, "Have a safe trip."
"In many respects,” says Heidenberger, “you can say I'm in denial now, still, because I still look periodically at the side door of the house, thinking that she'll come back."
To keep Michele's memory alive, Heidenberger took part in a 33-day cycling trip across the United States in April -- one day for each crewmember that perished at one of the three crash sites.
"Something positive has to come out of this. Simply put, we can't let the sacrifice of the 184 victims here at the Pentagon, nor the 3,000 victims who died on that day. We can't let it go in vain," he says.
It's the same feeling that drives Rosemary Dillard. Her husband Eddie was aboard American Flight 77.
"He was sitting in seat 5-B and the hijackers were in 5-E and 5-F. We were married 15 years. He was a good man, an honorable man, a good man."
Like many who lost loved ones, Rosemary has dedicated herself to making sure the victims of 911 are never forgotten. Rosemary has worked tirelessly to raise money to build a memorial to honor the 189 people who died at the Pentagon. "My purpose is that this memorial will be here and it will be here for a hundred years."
"Time heals things but I think, in this particular type of situation, I don't know if we'll ever heal completely,” says Major Stout.
"And the days that are most difficult for me,” admits Heidenberger, ”are the mornings when there's not a cloud in the sky," recalling the conditions on the day of the attack.
And for Rosemary Dillard, a question that has haunted her for the last five years is, "How could that happen on one of God's most beautiful days? How could that happen?"