Gabby Petito's best friend says Brian Laundrie once lived in the Appalachian mountains by himself 'for months'

• Gabby Petito's best friend Rose Davis said Brian Laundrie can survive in the wilderness.

• Davis told People that Laundrie once stayed in the Appalachian mountains by himself "for months."

• "He is out in the wilderness, I promise you," she said.

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Gabby Petito's best friend Rose Davis says Brian Laundrie can survive out in the wilderness because he has done it before. Davis told People in an interview that Laundrie, who is a person of interest in his fiancée Petito's death, once stayed in the Appalachian mountains by himself "for months."

"He is out in the wilderness, I promise you," Davis, 21, told People. "He's out there. He is. If he's alive, he's out there, camping out ... He lived in the Appalachians by himself for months."

Petito, 22 years old, was reported missing on September 11 by her mother, Nicole Schmidt.

Petito and Laundrie had been traveling around the US in a van and documenting their experience on social media, but he returned to their home in Florida without her.

This week, the FBI's Denver office confirmed on Twitter that human remains were discovered in a remote area in Bridger-Teton National Forest in Wyoming, and they belonged to Petito. They ruled her death a homicide.