(CNN) — The investigation into the disappearance of Brian Laundrie, whose fiancée Gabby Petito was found dead in a Wyoming campground last month, has uncovered new details about his earlier movements as well as traces of human activity at the nature reserve that’s been the focus of a massive search.

Police found the remnants of a campsite that appeared to be used recently in the Carlton Reserve, a sprawling 24,565-acre wilderness near the family home in Florida that has been closed to visitors, a source close to the family told CNN’s Chris Cuomo on Wednesday.

Laundrie’s father had been asked to show law enforcement the trails at the reserve, which his son had been known to use, the source said. But because of the campsite discovery, police restricted the search on Wednesday and did not include his father.

Additionally, the North Port Police Department confirmed that a notice was placed on an abandoned vehicle belonging to the Laundrie family near the nature reserve on September 14.

Laundrie’s family told police on September 17 that they had not seen him in days, saying he told the family he was headed to the reserve.

The search for Laundrie escalated as police investigated the disappearance of Petito, who was reported missing by her family on September 11. Petito and Laundrie had embarked on a cross-country road trip over the summer before Laundrie returned home to Florida, and Petito’s remains were later found in Wyoming.

The coroner’s initial determination for Petito’s manner of death was homicide, the FBI said.

While Laundrie has not been charged in her death, he is the subject of a federal arrest warrant for unauthorized use of another person’s debit card in the days after Petito last spoke with her family.

Abandoned vehicle was retrieved near reserve

The abandoned vehicle notice was placed on a Ford Mustang belonging to the Laundrie family outside the Myakkahatchee Creek Environmental Park on September 14, North Port police said Wednesday. The park acts as an entrance to the Carlton Reserve, not far from the family home in North Port.

Steve Bertolino, the attorney who represents Laundrie and his parents, Chris and Roberta Laundrie, told CNN that upon further communication with the FBI, “we now believe the day Brian left to hike in the preserve was Monday September 13.” His parents had previously told authorities he had left on September 14.

Chris Laundrie went to look for his son on the night of September 13 when he didn’t return from the park, Bertolino told CNN on Wednesday.

The next day, Brian’s parents returned to the area to look for Brian and saw the citation on the car, Bertolino said.

The parents returned again the next day, September 15, to retrieve the vehicle.

“The Laundries were basing the date Brian left on their recollection of certain events. Upon further communication with the FBI and confirmation of the Mustang being at the Laundrie residence on Wednesday September 15, we now believe the day Brian left to hike in the preserve was Monday September 13,” Bertolino said.

Bertolino told CNN that Chris Laundrie was asked to help North Port police search for him Wednesday but police had to postpone.

“Since the preserve has been closed to the public Chris has not been able to look for Brian in the only place Chris and Roberta believe Brian may be,” Bertolino said. “Unfortunately North Port police had to postpone Chris’ involvement but Chris and Roberta are hopeful there will be another opportunity to assist.”

CNN asked Bertolino whether Brian’s parents believe he’s in the reserve or another area. “No, they don’t believe he’s in another area. They believe he is in the preserve,” Bertolino said.

Regarding the campsite found and the family’s involvement in the search, the North Port Police Department told CNN the FBI is the lead agency in the case and that North Port police would not be making those decisions or taking those actions.

“The FBI would have to answer if that was true,” said North Port police spokesperson Josh Taylor.

CNN has reached out to the FBI for comment.

‘I want to see him in a jail cell for the rest of his life’

Petito’s body was found about a five-to-ten-minute walk from where her van was last seen near the entrance to the Grand Tetons, on the border of Bridger-Teton National Forest, according to her mother Nichole Schmidt and stepfather Jim Schmidt during the second installment of an exclusive interview with the “Dr. Phil” show that aired Wednesday.

Gabby’s body was in a clearing and was just in front of the remnants of a fire ring, Jim Schmidt said. “You could see where the rocks had been moved to make the fire ring,” he said.

“It’s definitely not an area that was heavily trafficked,” he added.

Jim Schmidt left a memorial and sunflowers at the site, CNN has previously reported.

The Schmidts were joined by Gabby’s father, Joe Petito, and his wife Tara Petito, along with their attorney Richard Stafford, for the interview with host Phil McGraw.

Joe Petito said he wants Laundrie found alive so he can spend his life behind bars.

“I want to see him in a jail cell for the rest of his life where — he’s an outdoorsman — being in that concrete cell and he can’t go see those trees and hug — and smell the fresh air like that,” Petito said.

“I want to look him in the eyes,” Nichole Schmidt said.

Laundrie family attorney Bertolino declined to comment Wednesday on the “Dr. Phil” interview.

In late September, Laundrie’s parents released a statement through their attorney, saying, “Chris and Roberta Laundrie do not know where Brian is. They are concerned about Brian and hope the FBI can locate him. The speculation by the public and some in the press that the parents assisted Brian in leaving the family home or in avoiding arrest on a warrant that was issued after Brian had already been missing for several days is just wrong.”

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