Brian Laundrie was 'grieving' when he vanished, days before Gabby Petito found dead, family's lawyer says

More than a month before authorities found the decomposed remains of Florida fugitive Brian Laundrie in a swamp near his home, he allegedly slipped away from his parents’ house under the guise of a hike.

That was on Sept. 13, two days after Laundrie’s fiancée, Gabby Petito, was reported missing. His attorney, Steve Bertolino, told Fox News Digital Thursday that he immediately informed the FBI that his client had failed to come home.

However, local police in North Port, Florida, said they thought Laundrie was still inside the house until they knocked on the front door on Sept. 17.

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Bertolino said that after he told the FBI that Laundrie failed to return from the park, he had no further contact with the FBI until they told him Friday about a tip that Laundrie had been seen in Tampa.

But from Tuesday evening to Thursday, neither Laundrie’s parents nor his attorney followed up with the FBI or local authorities about their missing son’s whereabouts.

"There was never any communication between myself and law enforcement in the next three days," Bertolino told Fox News Digital. "They never asked me, and I never informed them that Brian didn't come home."

They also waited until the Friday meeting regarding the Tampa tip to file a missing person report.

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"North Port PD was under the assumption that Brian was home, and so was the FBI when they got a tip on Friday that Brian was in Tampa, and they wanted to meet with us on Friday," Bertolino said. "I was shocked and said, 'That's good. You found him in Tampa,' and they said, 'What do you mean? I thought he's at the house.' I said, 'No, I told you the other day he never came home.'"

North Port Police Chief Todd Garrison had said in the middle of that week that he knew exactly where Brian Laundrie was – but he was wrong. 

Speaking to reporters during a news conference on Sept. 16, Garrison was asked if he knew where Laundrie was at that moment.

"Yes," he replied.

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The family made no effort to correct him and showed no public urgency about their son's whereabouts or well-being -- even though Bertolino later told ABC News that Brian’s father, Chris Laundrie, believed his son was "grieving" and upset when he left for the Sept. 13 hike. The public didn't know Petito was dead until authorities said they found her remains on Sept. 19.

Bertolino did not immediately respond to a request for clarification about Brian Laundrie’s mental state when he left or what he was "grieving" about.

Laundrie and Petito set off on a cross-country road trip earlier this year in a white Ford Transit van, which they lived out of as they camped at public parks along the way.

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An FBI-led search found Petito’s remains at a Bridger-Teton National Forest campsite on Sept. 18 north of Jackson, Wyoming. Teton County Coroner Dr. Brent Blue later ruled her death a homicide by manual strangulation – meaning she’d been killed by hand.

A travel-blogging couple known as Red, White and Bethune spotted Petito’s van at the campsite on Aug. 27 – hours after what may have been the last time she was seen alive in public.

That day, Nina Celie Angelo and Matthew England were eating at Merry Piglets in Jackson when they saw Brian Laundrie arguing with restaurant staff, they told Fox News Digital last month.

Laundrie exited and reentered about four times, and Petito apologized to the workers for his behavior, the couple said.

Two weeks before that, witnesses in Moab, Utah, told police they’d seen Brian Laundrie slapping and hitting Petito outside an organic grocery store. He also allegedly threatened to take her phone and drive off without her before police pulled the couple over north of town.

Despite a Utah law requiring arrests or citations to be made in all domestic violence cases, police deemed the matter a "mental health break" and told the couple to spend the night apart. Moab officials later announced an investigation into the officers’ handling of the matter.

Read updates at FOXNews.com.