Gabby Petito’s parents will appear on the “Dr. Phil” show on Tuesday to discuss the murder of their 22-year-old daughter and their frustration with Brian Laundrie’s family for ignoring their efforts to find out what happened.

According to the show’s website, Nichole Schmidt and Joe Petito will appear in two-part episode this week, as they reveal for the first time that they initially believed both Gabby and Brian were missing on their cross- country road trip. As CrimeOnline previously reported, Schmidt last spoke with her daughter via FaceTime in late August, and reported her missing on September 11 — though Gabby’s parents wanted a formal missing persons report earlier.

“We actually thought that they were both missing at that time,” Joe Petito said, according to the show’s website. The concerned parents tried calling the Laundries to learn what might have happened, but Brian’s parents ignored them, they said.

“It’s infuriating,” Nichole Schmidt said. “We didn’t actually know the van was in Florida at the time we contacted [Brian’s mother]. I was just worried that I hadn’t heard from Gabby.”

In a clip obtained by the Daily Mail, Joe Petito indicates that he believes Brian Laundrie is alive and intentionally evading authorities.

“He’s a coward…Anyone who lived in [the Laundrie] house is a coward,” Joe Petito said. “They don’t know how to stand up for their actions.”

Watch a preview clip of the Petito family on “Dr. Phil” at the DailyMail.