In his final words, Brian Laundrie admitted to killing his former fiancée Gabby Petito in a remote Wyoming campground, according to the FBI, based on entries investigators found in the notebook recovered near his skeletal remains in a Florida swamp.

Investigators found the admission in his notebook, which spent weeks underwater as flooding delayed the recovery effort.

"A review of the notebook revealed written statements by Mr. Laundrie claiming responsibility for Ms. Petito’s death," the FBI revealed Friday, roughly three months after Laundrie’s body surfaced at the Myakkahatchee Creek Environmental Park, about 10 minutes from his parents’ home in North Port, Florida.

Chris and Roberta Laundrie at Myakkahatchee Creek Environmental Park in Florida on October 20, 2021

Chris and Roberta Laundrie at Myakkahatchee Creek Environmental Park in Florida on October 20, 2021 (Michael Ruiz/Fox News Digital)

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The FBI said that it ultimately found no other people aside from Laundrie as "directly involved in the tragic death of Gabby Petito."

In a statement, Petito’s parents thanked the FBI and state and local authorities who worked on the case.

"We truly appreciate the FBI’s diligent and painstaking efforts in this extremely complicated case," they said through their attorney, Rick Stafford. "The quality and quantity of the facts and information collected by the FBI leave no doubt that Brian Laundrie murdered Gabby."

On Oct. 20, Laundrie’s parents Chris and Roberta left their home before dawn and drove to the swamp, where the floodwater had receded after blanketing the area for weeks.

With two law enforcement officers and a Fox News Digital reporter present, they returned to the area where their lawyer said they had been directing authorities to search since mid-September.

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Chris Laundrie zigzagged through the brush and eventually stumbled upon a drybag in a clearing. The parents passed within just a few yards of where law enforcement would separately find their son’s remains that same morning.

Authorities also found a revolver. And days later, a group of protesters who had been demanding answers from the Laundrie parents spotted Petito’s water bottle in the same clearing.

It would be weeks before a forensic investigation on the badly decomposed remains concluded that Laundrie’s cause of death had been suicide by a self-inflicted gunshot wound. They confirmed his identity through dental records and DNA.

And it took months for the FBI to reveal details about what the notebook held inside – or to acknowledge that they’d found the gun. Laundrie’s parents, despite holding the bag in their hands, were kept in the dark until the investigation closed, according to their attorney, Steve Bertolino. The notebook has not yet been returned to the family, he said.

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"I don’t think they realized what it was when they found it at the time," he said.

At one point, they handed the bag to a North Port detective. He told them about the human remains and sent them home.

Roberta Laundrie wiped a tear from her husband’s eye. They left.

A North Port, Florida, detective makes a phone call from the entrance of Myakkahatchee Creek Environmental Park on Oct. 20, 2021.

A North Port, Florida, detective makes a phone call from the entrance of Myakkahatchee Creek Environmental Park on Oct. 20, 2021. (Michael Ruiz/Fox News Digital)

BRIAN LAUNDRIE FOUND: PARENTS MAY HAVE JUST MISSED UNCOVERING REMAINS THEMSELVES

Then the detective tossed the bag on the ground near the park entrance before authorities closed the park to the public.

Petito and Laundrie set off on a cross-country vanning trip last June. She wanted to blog about her travels. He didn’t support her, according to police documents in Moab, Utah, where the couple got into a fight in public on Aug. 12. This incident was first reported by Fox News Digital.

Two weeks later, Petito’s idyllic Instagram posts stopped appearing. By the end of the month, her mother had received a text message from her daughter’s phone that she didn’t believe was real.

A still from one of Petito's travel-blogging videos.

A still from one of Petito's travel-blogging videos. (Gabby Petito/YouTube)

When the FBI released its final statement on the case Friday, investigators also said that Laundrie had attempted to mislead them by holding a fake text conversation with himself, using Petito’s phone.

"The timing and content of these messages are indicative of Mr. Laundrie attempting to deceive law enforcement by giving the impression that Ms. Petito was still alive," the FBI said.

Police in Petito’s New York hometown, who had opened the initial missing person investigation, said they had no comment Friday.

Reporters witnessed a rainbow overhead just moments after authorities removed Gabby Petito's remains from a campsite in Wyoming's Bridger-Teton National Forest.

Reporters witnessed a rainbow overhead just moments after authorities removed Gabby Petito's remains from a campsite in Wyoming's Bridger-Teton National Forest. (Audrey Conklin/Fox News Digital)

Police in North Port, where Petito and Laundrie had lived before setting off on their trip, said they hope the FBI's findings "provide some closure."

The FBI took the helm in September and was leading the search for Petito’s remains when crews found her at a dispersed camping area in Bridger-Teton National Forest, north of Jackson, Wyoming, on Sept. 19. The Teton County coroner ruled her death a homicide by blunt-force trauma to the head and neck and manual strangulation.

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They found her after a tip from another travel blogging couple, Jenn and Kyle Bethune, saw Petito’s distinctive white Ford Transit van on their own dashcam video from a trip through the area in late August, around the time Petito was last seen alive.

Laundrie left Petito's body in the wilderness and drove her van to his parents' house in Florida. Then he said nothing about her disappearance before ducking off into the swamp once her missing person case made international headlines.

"The public’s role in helping us in this endeavor was invaluable," FBI Denver Special Agent in Charge Michael Schneider said in a statement Friday. "On behalf of the FBI, I want to express my deepest appreciation to the public for the thousands of tips that were provided during the investigation, and to our local, state and federal law enforcement partners for their work throughout the investigation."

Fox News' Stephanie Pagones contributed to this report.