Gabby Petito's family urges missing fiancé Brian Laundrie: "Turn yourself in"

The family of Gabby Petito and their attorney thanked law enforcement on Tuesday and asked her fiancé, Brian Laundrie, a person of interest in her disappearance, to turn himself in to authorities. Laundrie, who police said was initially uncooperative in the investigation, has been missing since he was declared a person of interest.

"The Laundries did not help us find Gabby, they're sure as not going to help us find Brian. For Brian, we're asking you to turn yourself in to the FBI or the nearest law enforcement organization," said attorney Richard Stafford, speaking on behalf of the family at a news conference.

Petito, 22, and Laundrie, 23, were taking a months-long cross-country road trip when Petito was last seen. During the trip, a witness called police to report that the couple was in a domestic dispute, but responding officers classified the event as more of a mental health break and separated the two for the night. 

Petito was reported missing on September 11, after Laundrie returned home to Florida without her in their 2012 Ford Transit van. 

The FBI later confirmed a body found in Wyoming was identified as Petito, and an initial autopsy ruled her cause of death a homicide.

On Tuesday, her parents also showed off new tattoos in memory of Petito, including ones based on a design Petito drew and one she had that say "Let it be" and "Believe."

"Our focus is still on mourning Gabby and honoring Gabby. The FBI is doing everything they can and we have our full faith in them," said her stepfather, Jim Schmidt.

Police have been searching for Laundrie in dense swampland in Florida, and the FBI issued an arrest warrant for Laundrie, charging him with unauthorized use of a bank card for allegedly withdrawing sums of money around the time Petito went missing. The FBI visited the home of Laundrie's parents on Sunday and removed personal items belonging to the missing man, Laundrie family attorney Steven Bertolini confirmed to CBS News.

Rose Davis, a friend of Petito, told CBS News that Laundrie is comfortable in the outdoors, which led her to believe he may be hiding in the woods. 

"He's good with nature. He can go into nature," Davis told "48 Hours." So, my first thought was he's — he's in the woods. He's somewhere in the woods."

Laundrie's parents said in a statement Monday that they do not know where their son is and have not helped him hide from authorities. 

"Chris and Roberta Laundrie do not know where Brian is," the statement said. "They are concerned about Brian and hope the FBI can locate him. The speculation by the public and some in the press that the parents assisted Brian in leaving the family home or in avoiding arrest on a warrant that was issued after Brian had already been missing for several days is just wrong." 

Family and friends of Gabby Petito gathered for a memorial service Sunday on Long Island, in a service that drew hundreds of people after her family opened it to the public.

"We've received letters, emails, cards, from all over the world. From Australia, from Europe; we had people from Italy. We had people at the funeral that came from as far away as Texas, as Florida, as California. People from all over the country have called and sent their well wishes," Stafford said. 

Stafford also said Tuesday that the family will form the Gabby Petito Foundation. 

"We need positive stuff to come from the tragedy that happened. We can't let her name be taken in vain. We need positive stuff, so anything that we can do to bring that up and help people, that's what we want to do," said her father, Joe Petito.