Brian Laundrie's parents may have already spilled what they know about Gabby Petito's murder to the FBI to avoid obstruction charges, law enforcement experts have told DailyMail.com.
Christopher and Roberta Laundrie joined the hunt for their fugitive son Wednesday and within hours cops had finally located his backpack, notepad and possible remains in Florida swampland.
Authorities said the breakthrough - five weeks into the manhunt - came after receding water levels allowed greater access to some of keen hiker Brian's favorite trails and hangouts in the alligator-infested Carlton Nature Reserve.
But former FBI agent Stuart Kaplan thinks authorities issued the Laundries with a behind-the-scenes ultimatum: help us find Brian or face years behind bars yourselves.
Roberta Laundrie was last seen in exclusive DailyMail.com photos Wednesday after she and husband Chris returned from the Carlton Reserve where human remains were found
Law enforcement experts tell DailyMail.com it's possible Chris and Roberta - who have remained tight-lipped on son and person of interest Brian Laundrie - are finally speaking up after being given an ultimatum
The couple has come under scrutiny since their son went on the run after Gabby Petito's body was found. Pictured: Chris Laundrie returns home Wednesday
'There's no doubt that Brian Laundrie's parents are fully engaged with law enforcement,' Kaplan told DailyMail.com.
'I do believe that there was some sort of agreement where they accepted immunity in exchange for their full cooperation.'
Despite a rash of unconfirmed sightings across the US, police and FBI search teams had maintained a laser focus on the sprawling Carlton Reserve ever since Laundrie, 23, was reported missing by his parents on September 17.
Gabby's remains were found two days later at the Spread Creek Dispersed Camping Ground in Grand Teton National Park.
The 22-year-old travel vlogger's death was declared a homicide by strangling and Laundrie - who came home from a cross-country road trip without her on September 1 - remains the only confirmed person of interest.
'I think from the very beginning that Brian Laundrie's parents were torn between wanting to protect their son and not wanting to cross a line that would put them in the crosshairs of law enforcement,' added Kaplan, now a criminal defense lawyer.
Brian Laundrie, 23, is the sole suspect in the murder of his 22-year-old fiancee Gabby Petito. Her strangled body was found in September, weeks after she was last seen alive. The pair were on a cross-country camper van trip when she vanished and he went home in September
Christopher, 62, and Roberta, 55, initially told the North Port Police Department they last saw their son when he headed off to go hiking at the reserve on September 14
Former FBI agent Stuart Kaplan says he believes 'there was some sort of agreement where they accepted immunity in exchange for their full cooperation'
'If you lie to a federal agent, mislead them or give them false information that can lead to prosecution for obstruction of justice and you could be looking at five years in jail. And it's an easy trap to fall into.'
Christopher, 62, and Roberta, 55, initially told the North Port Police Department they last saw their son when he headed off to go hiking at the reserve on September 14, leaving his Ford Mustang parked nearby and never returning to it.
The couple came under renewed scrutiny, however, when they suddenly 'revised' their timeline, saying through their attorney, Steven Bertolino, that they last saw him on the evening of September 13.
'The probability is strong that it is Brian's remains, but we're going to wait for the forensic results to come in and verify that,' Bertolino told CNN on Wednesday night.
He said Christopher and Roberta would wait until a final determination was made before making any comment.
To date the couple have not said a single word publicly about Brian and Gabby, who got engaged last year and lived under their roof before they headed off in July for a road trip in a converted van.
Chris and Roberta Laundrie (pictured) alerted investigators on Tuesday night that they intended to search Myakkahatchee Creek Environmental Park for their son on Wednesday morning. The FBI and North Port Police Department agreed to meet them at the park
A police officer is pictured walking in the Carlton Reserve with what appears to be the dry bag discovered by Laundrie's father in the preserve. The discovery was made on Wednesday, five weeks after he went on the run following the disappearance of his fiancée Gabby Petito. She was found strangled to death in September in Wyoming
The Sarasota County Medical Examiner's Office was at the scene Wednesday after human remains were found. It's unclear how long it may take for the remains to be formally identified
Pictured: A map showing the location of where Laundrie's belongings were found near a bridge connecting the the Myakkahatchee Creek Environmental Park and the adjoining Carlton Reserve, in relation to the Laundrie family home in North Port, Florida (pictured bottom right). The home is located around four miles south of where the belongings were found
Retired FBI agent Jennifer Coffindaffer told DailyMail.com that if Laundrie's parents knew his whereabouts, they could be vulnerable to aiding and abetting charges but cautioned that authorities would need compelling evidence in the event Brian was confirmed dead.
'That evidence could include text messages telling him to run or telling him they were going to destroy evidence,' Coffindaffer speculated.
'There's no blood involved in a strangulation but there could be some cells on his clothing. I think the strongest possibility would be an obstruction charge on the cleaning of the Petito van.'
Without such evidence there is nothing, however, that prosecutors can do to force Christopher and Roberta Laundrie into revealing what Brian told them in the 12 days he spent at home before disappearing under the noses of police.
'They can't be compelled. But you would hope, especially since now that it appears their son is dead, that if they are decent people they will disclose what they know,' Coffindaffer added.
DailyMail.com spotted Brian Laundrie's parents on a five-hour shopping trip Tuesday morning
They also refused to answer DailyMail.com's inquiries of 'is he in the park, did you help him get there?' in reference to the massive swampland search for survivalist Brian, 23, that started nearly five weeks ago at the alligator-infested Carlton Reserve near North Port
'The guilt builds and I would not be surprised at all if one of them came forward, eventually, although it could take a long time.'
At a briefing Wednesday afternoon FBI Special Agent in Charge Michael McPherson confirmed that human remains had been found in an area of the 24,000-acre Carlton Reserve that was previously submerged in water.
The reserve has been reopened to the public but Bertolino told NewsNation that he contacted police on Tuesday to tell them the Laundries wanted to resume the search personally now that the water level had receded.
Christopher had previously joined investigators to look for his son but this was the first time he was accompanied by his wife.
Bertolino said the
