Richard Drew, a photographer for nearly six decades, has learned a basic rule: “You can be two hours early, but not a 60th of a second late. In other words, if you’re not present when it happens, you can’t photograph it.”

Drew, who has been with the Associated Press for 51 years, was there in time to photograph Frank Sinatra escorting Jackie Onassis… Muhammad Ali lands a knockout punch… and Ross Perot bursting into the 1992 presidential race in such a way that the pepper pot billionaire was so captivated. But he was not at the World Trade Center at 8:46 a.m. or 9:03 a.m. on September 11, 2001, when the planes hit the towers. He was on assignment at a maternity fashion show in Midtown when his office called calmly, “‘A plane has hit the World Trade Center,'” he recalled.

When he wasn’t chasing breaking news, he learned to put himself in places where it might happen.

On June 5, 1968, he made the decision to attend a speech by presidential candidate Robert F. Kennedy at the Ambassador Hotel in Los Angeles. “The office had no idea I was there; I just assigned myself to this job,” he explained. Drew entered the kitchen in search of a glass of water. Robert F. Kennedy was also present. A gunman was also present.

Drew climbed onto a table and photographed the chaos as the 42-year-old junior senator lay on the ground. Drew and the other photographers were approached by Kennedy’s wife.

“I didn’t take the picture,” Drew explained. The photograph of the falling man was taken by the camera. And then, as these people fell, I’d put my finger on the camera’s trigger and hold the camera up, photographing and following them as they fell, and the camera would open and close and take the pictures as they fell. I have, I believe, eight or nine frames of this gentleman falling, and the camera happened to cycle at a time when he was completely vertical. I didn’t notice the picture until I got back to the office and began looking through my files on my laptop. “I didn’t notice it.”

Drew’s photograph, which became known as the “Falling Man,” was published in a number of newspapers the following day. Many people were taken aback by the lonesome vision.

One prominent viewer was captivated by its deeply human pull. Sir Elton John told “Sunday Morning” correspondent Anthony Mason five years ago that he needed to buy the photograph for his personal collection. “It’s not a shot that many people would want to hang on their wall,” John explained.

It captures, perhaps more than any other image, the horror of that day twenty years later.

The identity of the fallen man has never been determined, though two possibilities have been proposed by journalists. On the parapets of the 9/11 Memorial, their names, Jonathan Eric Briley and Norberto Hernandez, are only one name apart.

Drew, on the other hand, was able to assist in the identification of another victim that day: “I can’t remember how many actual people I photographed during it, but it wasn’t just one or two people. A gentleman called and stated that he knew what his fiancée was wearing that day and that they had not recovered her body or anything else. And he was curious if he could look at my photos. I actually sat with him on my laptop and we went through the video of the people falling from the building frame by frame. And he noticed it. ‘Oh, that’s her,’ he said. And that was the end of it.”

Drew photographed the aftermath of the attack for a month after it happened: “And my cell phone rang. It was also my daughter. ‘Dad, I just want to tell you that I love you,’ she says. And to this day, no matter where I am, she calls me on September 11th to say, ‘Dad, I love you,’ because I might not have survived.”