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STORY: Amid a strong buzz, stars Casey Affleck and Rooney Mara arrived in Park City, Utah for the premiere of "Ain't Them Bodies Saints," at the Sundance Film Festival on Sunday (January 20).

The stars graced the premiere line for the film, along with director David Lowery.

Affleck, the younger brother of Ben Affleck, called making the film both challenging and rewarding.

"We shot in Louisiana mostly and it was a lot of fun," explained Affleck, on the film that tells the story of two Texas outlaws on the run.

"It's 165 degrees most days but it was really small crew. And like a lot of these movies here at Sundance, they kind of have the same spirit. The movie had gone through the Sundance lab for writer, director and producer and so coming in to it I already had that spirit of being a tight knit group, little crew that wanted to do things in a very traditionally independent way. Small in scale all the way around, which I love to do and it's a fun way to work."

Actress Rooney Mara, who most recently worked in "The Girl with the Dragon Tattoo" and "The Social Network," also found the indie film experience rewarding.

The Sundance Film Festival runs from January 17 through January 27 in Park City, Utah.