Gabby Petito's family have made a stunning claim about Brian Laundrie's parents in an amendment to their lawsuit filed against the couple.
Earlier this year, Ms Petito's parents filed a lawsuit claiming the Laundrie family knew where the 22-year-old's body was.
Ms Petito and Laundrie had set off on a van holiday together last year, only for Ms Petito to be reported missing. Her family last heard from her in August.
Laundrie returned home to Florida without his partner. After she was reported missing, she was found dead in Wyoming on September 19. A manhunt then ensued to find Laundrie after he disappeared.
In the amendment to the lawsuit, Ms Petito's family claim the Laundrie family went on a holiday in Florida, while they were distraught and trying to locate her.
The lawsuit alleged the Laundrie's went to Fort De Soto Park with the knowledge Laundrie had murdered Ms Petito, CNN reported.
"They went on vacation knowing that Brian Laundrie had murdered Gabrielle Petito, it is believed that they knew where her body was located, and further knew that Gabrielle Petito's parents were attempting to locate her," the amended lawsuit reportedly says.
The Laundrie family did go to the Fort De Soto Park campground on September 6 and then left as a family on September 7.
The dates the family stayed at the campground were confirmed by a check-in report obtained by CNN.
The FBI confirmed in January this year Laundrie claimed responsibility for Ms Petito's death in the suicide note.
By the time Laundrie's remains were found on October 20, he had been missing for over a month.
He disappeared on September 13, days after his family returned from their holiday at Fort De Soto Park.
Laundrie family 'acted with malice'
In the early days of the investigation, Ms Petito's family publicly pleaded with the Laundrie family to help find her.
On September 16, days after Ms Petito's family reported her as missing, the Petito family attorney Richard Stafford read a letter to the Laundrie family at a news briefing.
"We haven't been able to sleep or eat, and our lives are falling apart," the letter said.
The updated lawsuit now includes details of how father Joseph Petito and mother Nichole Schmidt were suffering mentally by not knowing where their daughter was.
It claims Christopher and Roberta Laundrie knew Ms Petito's parents were suffering with each passing day.
“Christopher Laundrie and Roberta Laundrie further knew that they could prevent such additional mental suffering and anguish of Joseph Petito and Nichole Schmidt by disclosing what they knew about the well-being and location of the remains of Gabrielle Petito, yet they repeatedly refused to do so," it says, according to WFLA.
"In doing so, Christopher Laundrie and Roberta Laundrie acted with malice or great indifference to the rights of Joseph Petito and Nichole Schmidt.”
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