When President George W. Bush learned that two planes had barreled into the World Trade Center buildings on Sept. 11, 2001, he was sitting in front of a group of children who were reading aloud. So as to not cause alarm, he remained calm and stoic. And for it, he received much flak.

But now, in an interview with the National Geographic Channel, Bush is explaining his reaction and what was going through his mind when he was told a second passenger jet had hit one of the WTC buildings.

"My first reaction was anger. Who the hell would do that to America? Then I immediately focused on the children, and the contrast between the attack and the innocence of the children," Bush said.

When his Chief of Staff Andy Card walked behind him and whispered in his ear, "a second plane has hit the second tower. America is under attack," Bush said he knew a lot of people would be watching for his response.

"So I made the decision not to jump up immediately and leave the classroom. I didn't want to rattle the kids. I wanted to project a sense of calm," he said. "I had been in enough crises to know that the first thing a leader has to do is to project calm."

 "George W. Bush: The 9/11 Interview" will debut on Aug. 28, as part of a series of programs marking the 10th anniversary of the attacks.

Bush also described what it was like to walk through the wreckage of Ground Zero, The Washington Post reported.

"From the air, it looked like a giant scar. But when I actually got to the site, it was like walking into hell," he said. "One of my concerns, like the concerns of other husbands and wives, was, 'Was my spouse OK? Was Laura OK? And my second concern was, 'Were our girls OK?'"

The two-day interview started the day after President Barack Obama announced the killing of 9/11 mastermind Osama bin Laden. That news, Bush said, made him "grateful," but he didn't "feel any great sense of happiness. Or jubilation. I felt a sense of closure. And I felt a sense of gratitude that justice had been done."

The program will also feature archival footage shot at the Pentagon and in New York days after the attacks from the George W. Bush Presidential Library -- footage never before shown to the public.

Until now, the former President has never discussed his personal state, or what drove his decisions in the immediate aftermath. It is also the first time Bush has spoken on the death of bin Laden.

"There were no politics, no agenda as he recalled what happened that day. What you hear is the personal story of a man who also happened to be our president," said Peter Schnall, the documentary's produced and director. "Listening to him describe how he grappled with a sense of anger and frustration coupled with his personal mandate to lead our country through this devastating attack was incredibly powerful.

"What surprised me most was his willingness to speak openly, candidly, and personally about the events of that day. There were no requests for questions beforehand, no editorial say from the President or his office," the Daily Mail reported.

Bush said 9/11 will be a day on the calendar, "like Pearl Harbor Day. For those of us who lived through it, it'll be a day that we'll never forget."