'Zero Dark Thirty': Bin Laden Manhunt Film Based on Controversial Firsthand Accounts: 'Nightline' Exclusive

Nov. 26, 2012— -- It was the greatest manhunt of all time, the stealthy nighttime raid by the elite SEAL Team Six on Osama bin Laden's compound in Pakistan, which led to the death of the world's most wanted terrorist leader.

It is the subject of "Zero Dark Thirty," a riveting new film by director Kathryn Bigelow and screenwriter Mark Boal, both of Oscar-winning "The Hurt Locker" fame. But when they began making a film about the hunt for bin Laden six years ago, right after they finished "The Hurt Locker," the movie they had in mind was about the failed attempt to find bin Laden in the Tora Bora mountains of Afghanistan.

That plan changed drastically on May 1, 2011 when bin Laden was killed. Boal, a meticulous investigative reporter, picked up the phone and started working his sources.

"It was a thrilling journey to go on and also thrilling to discover what the people who were involved in this mission were really like," Boal said.

In an exclusive interview with "Nightline," Bigelow and Boal talked about bringing "Zero Dark Thirty" to the screen based on Boal's interviews and Bigelow's dramatic vision. Raddatz first met the filmmaking duo while Bigelow and Boal worked on "The Hurt Locker" and had shared her insights with them about Afghanistan, where she has frequently reported.

"It was all based on first hands accounts so it really felt very vivid and very vital and very, very immediate and visceral of course which is very exciting as a film maker," Bigelow said.

Bigelow said she and Boal were working in his office when they heard President Obama's now famous announcement that the United States had "conducted an operation that killed Osama bin Laden."

"It was a personal moment for me because I grew up in New York City," Boal said. "I think for a lot of people, just kind of an overwhelming moment."

All of a sudden, Bigelow said it put their project in a very different perspective.

"It was not just as a film concern, it was kind of a global concern," she said. "We both realized simultaneously that we had to pivot."

"I picked up the phone and started calling sources and asking them what they knew and taking referrals and knocking on doors and really approached it as comprehensively as I could," Boal said.

Almost immediately, the filmmakers found themselves in the middle of an election year firestorm, accused of receiving classified documents to bolster the president's role. It's something they both deny.

"I certainly did a lot of homework, but I never asked for classified material," Boal said. "To my knowledge I never received any."

In fact, President Obama makes only a fleeting appearance in the film. The star of this real-life drama is, surprisingly, a young female CIA officer, played by Jessica Chastain, who helps find bin Laden through a long-forgotten courier.

"It was a couple of months into the research when I heard about a woman, part of the team, and she has played a big role and she had gone to Jalalabad and been deployed with the SEALs on the night of the raid," Boal said.

"When I realized at the heart of this hunt, at the heart of this 10-year odyssey was this woman, this young woman who had a kind of tenacity and a dedication and a courage, she would never say no, I was excited to take it on," Bigelow said.