NORTH PORT, Fla. (WFLA) — Family members of 22-year-old Gabby Petito, who went missing during a cross-country road trip she had been on with her fiancé Brian Laundrie, addressed Laundrie’s parents in a letter on Thursday that was read by a family attorney.

Attorney Rick Stafford, who represents the Schmidt and Petito family in New York, read the letter during a news conference Thursday afternoon. The letter, addressed to Laundrie’s mother and father, called on them to help find Petito.

“We understand that you are going through a difficult time and your instinct is strong to protect your son,” the letter said. “We ask you to put yourselves in our shoes. We haven’t been able to sleep or eat and our lives are falling apart.”

In their letter, Petito’s family accused Laundrie’s family of knowing where “Brian left Gabby” and begged them to share that information.

“As a parent, how could you let us go through this pain and not help us? As a parent, how could you put Gabby’s younger brothers and sisters through this?” they said. “Gabby lived with you for over a year. She’s going to be your daughter-in-law. How can you keep her location hidden?”

When asked about the newly-released body camera video from police that shows an incident between Petito and Laundrie in Utah, the attorney for Petito’s family noted that the FBI asked her family not to discuss the relationship between the young couple.

Earlier this week, Laundrie was identified by North Port police – the lead agency investigating the missing person case – as a person of interest. According to police, Laundrie returned home from the couple’s cross-country trip by himself on Sept. 1. Petito was nowhere to be found. Laundrie has since retained an attorney, who has said the family will “remain in the background.”

“We share the frustration with the world right now. Two people went on a trip. One person returned. And that person that returned isn’t providing us any information,” North Port Police Chief Todd Garrison said during a news conference earlier Thursday afternoon.

Petito’s father also spoke at the North Port police news conference, and also begged Laundrie’s family – as well as the rest of the public – for help.

“What I need from everybody here is help,” Joe Petito said. “Because the goal is still not met. And the goal is to bring Gabby home safe.”

“I’m asking for help from everyone here, I’m asking for help from everyone at home. I’m asking for help from the parents of Brian. I’m asking for help from the family members and friends of the Laundrie family as well,” he added. “Whatever you can do to make sure my daughter comes home, I’m asking for that help. There is nothing else that matters to me now.”