Gabby Petito's mom says she wasn't worried about her daughter's road trip because she thought Brian Laundrie would take care of her

• Gabby Petito's mother said she'd thought her daughter would be safe with her fiancé, Brian Laundrie.
• She told "60 Minutes Australia" she now wants to see Laundrie "in a cell for the rest of his life."

Gabby Petito's mother said she didn't worry about her daughter's road trip with her fiancé, Brian Laundrie, because she thought he would take care of Petito.

Nichole Schmidt made the remark in an interview with "60 Minutes Australia" that aired on Sunday. It was Schmidt's first interview since an autopsy found that Petito, 22, had died by strangulation.

Schmidt said she had supported Petito's dreams of taking a road trip across the country with Laundrie, whom Schmidt described as "polite and quiet."

"I told her to be careful, be safe, you know, make sure - to be aware of your surroundings, you know, don't trust everybody," she told "60 Minutes."

"But I felt safe because she was with Brian, and I felt like she would be OK," she said. "I thought he would take care of her."

Schmidt told "60 Minutes" that now, "I want to get him in a cell for the rest of his life."

Watch the full interview here:

Her husband, Jim Schmidt, Petito's stepfather, told the program that they wanted "vengeance" and "justice."

Petito's mother reported her missing on September 11, after Laundrie returned alone from the road trip. Laundrie, the person of interest in Petito's case, went missing in mid-September.

Authorities have been searching for Laundrie at the Carlton Reserve, a 25,000-acre nature preserve in Florida, but say they have not found any signs of him.

Survival experts told Insider that it was unlikely that Laundrie would be alive if he had been hiding out for so long.