Stories of resilience, survival make up new NatGeo documentary series '9/11: One Day in America'

LOS ANGELES -- Dozens of stories of resilience make up the new documentary "9/11: One Day in America." The series takes a deep dive into the heroism we saw on that day, recounting what took place 20 years ago, at times minute by minute - through first-person narratives of the first responders and survivors.

Filmmakers spent more than three years interviewing 54 people and learning their personal stories.

"You end up developing a relationship and a rapport through these first person accounts. That's really the primary purpose is to be able to build empathy, to humanize the events verses kind of thinking of them in a geo-political way, which has kind of become the narrative as time has gone on," said Executive Producer TJ Martin.

'I think we were keen to take a step back and make sure that it was very much people who experienced that day had their voices heard," said Executive Producer Caroline Marsden.

To create this docuseries, the filmmaking team sifted through almost 1,000 hours of archival footage - some of it, never seen before.

"I think the thing I'm most proud of is being able to create a space for those who had the courage to share their stories and honor those narratives," said Martin.

The series begins Sunday, Aug. 29, at 9p/8p and will air over four consecutive nights on National Geographic. Episodes will also be available next day on Hulu.