CNN Films said today it has acquired the Naudet brothers’ documentary 9/11 that first aired on CBS, ahead of the 15th anniversary of the attack on the World Trade Towers and the Pentagon.

The docu from French-born filmmakers Gédéon and Jules Naudet, who also executive produced with retired Manhattan firefighter James Hanlon, will be updated  to include a new introduction by Denis Leary, for broadcast on CNN worldwide. CNN Films will work with the team to update the film for the 2016 edition, and will retain worldwide broadcast rights for the film franchise and its archival material in perpetuity.

The project will be re-titled 9/11 Fifteen Years Later and will debut with limited commercial interruption, in back-to-back broadcasts, on Sunday, September 11, 2016, at 8 PM and 11 PM on CNN/U.S. On CNN International, it will premiere September 11 at 6 AM with encore broadcasts at 3 PM and 8 PM.

The Naudets were at the Duane Street New York Fire Department house on the morning of September 11, 2001, to film the training of a rookie New York firefighter, when hijacked American Airlines Flight 11 crashed into Tower One of the World Trade Center. An image of that moment of impact was filmed by Jules Naudet, and first aired that evening on CNN. Their completed film, however, debuted on CBS.

Separated throughout that day, and accompanying different members of the fire company, the brothers continued filming the rescue efforts of the first responders in what became a rough, gripping, minute-by-minute account of the attack, through the lens of the filmmakers who just happened to be on the scene at the time. Capturing the only video from inside the World Trade Center during the attack, the brothers kept filming from within and around Tower One during the collapse of both towers.

In the update, the filmmakers revisit some of the firefighters and their families. Daniel Nigro, New York City’s Fire Commissioner, answers questions about his department’s readiness in the event of another attack, particularly at the recently completed One World Trade Center, aka “Freedom Tower.”

Nancy Duffy, VP Program Development at CNN, Amy Entelis of CNN Films, and Ben Silverman of Propagate Content, are executive producers for CNN Films Presents 9/11 Fifteen Years Later; Courtney Sexton, VP Pprogram Development, and Jessica Velmans, senior producer, are supervising producers for the film.

The acquisition deal between CNN Films and Goldfish Pictureswas negotiated by Stacey Wolf, VP Business Affairs, and Kelly MacLanahan, senior legal counsel, both of CNN, on behalf of CNN Films, and by Silverman of Propagate and Lisa Davis of Frankfurt, Kurnit, Klein & Selz on behalf of the filmmakers.