The bombshell revelation was made by Mr Laundrie's father, Chris, during a deposition. He said on 29 August his son called him in a "frantic" state and told him that Ms Petito was "gone." He then asked his father to get him a lawyer, according to WFLA.
The Petito family has sued the Laundrie family, alleging they knew information about their daughter's location, but did nothing to assist in the nationwide search for the woman.
Ms Petito was found dead in the Bridger-Teton National Forest on 19 September after a nearly month-long search. Her cause of death was determined to be blunt force trauma to her head and neck and manual strangulation.
She had been travelling with her then-boyfriend, Mr Laundrie, on a van trip throughout the western US at the time of her death. Mr Laundrie returned home without her, soon spawning suspicions among her family that something had happened to her.
Mr Laundrie eventually slipped away from the police who had been dispatched to watch his home and hid out at a nearby nature preserve. He ultimately died by suicide in the preserve.
After another month-long search, police discovered Mr Laundrie's remains in the park, as well as a notebook containing a written confession that he killed Ms Petito.
Ms Petito's family has long suspected that Mr Laundrie's attorney and family members knew more than what they let on. Chris Laundrie's deposition all but confirmed to them that the family was withholding information about Ms Petito. They also suspected the family's lawyer had also withheld information.
On 17 October, the Laundrie's lawyer, Steven Bertolino, sat for a deposition and testified that Chris Laundrie spoke to his son.
The Petitos have filed a motion to try to force Mr Bertolino to testify. He has been resistant, citing attorney-client privilege. The motion argues that Mr Bertolino cannot claim attorney-client privilege on behalf of himself or on behalf of Mr Laundrie, who they argued waived his privilege by confessing to the murder in the note found among his remains.
“Clearly, Brian Laundrie had no such expectation of privacy in authorizing a confession and leaving it in his backpack to be found following his death,” the motion argues.