They say dog is man’s best friend, and sometimes he’s a hero. Those sentiments were forever solidified in the hours and days following the attacks on our nation on September 11, 2001.

Genelle Guzman-McMillan, like thousands of her fellow Americans that day, was working in her office in Tower One of the World Trade Center, when suddenly she heard a horrific sound outside. She knew she needed to get out. And fast. As she raced down the stairwell, along with 15 of her Port Authority co-workers, all trying to get to the ground floor, the building collapsed around her.

“I felt the walls cave in,” she later recalled for a documentary produced for Animal Planet. “It was dark and everything was rumbling.”

Pinned amidst a makeshift coffin of steel and cement blocks, Guzman-McMillan was unable to move. She lay trapped there for 27 long hours, praying, until the morning of September 12th…when help arrived in the form of a four-legged savior: A German shepherd named Trakr, who’d traced her scent, leading rescuers to her.

“It’s so awesome that the dogs could have this kind of sense, to find people buried under the rubble,” Guzman-McMillan told Animal Planet for the new documentary “Hero Dogs of 9/11.” “I felt total renewed life in me…That was the most joyful moment.”