The agency, closing a high-profile case, said that a notebook found near Mr. Laundrie’s body included statements in which he confessed to killing his fiancée.
Brian Laundrie claimed responsibility for killing his fiancée, Gabrielle Petito, the Federal Bureau of Investigation said on Friday, as it prepared to close a case that had galvanized social media and prompted widespread sleuthing by amateur detectives.
The F.B.I. disclosed that a notebook that was found near Mr. Laundrie’s body in October included a written confession, as the agency provided what it called a final investigative update on a case that had drawn thousands of tips from the public and engaged law enforcement agencies across the country.
The F.B.I. did not reveal details of the incriminating statements other than to say that the notebook contained “written statements by Mr. Laundrie claiming responsibility for Ms. Petito’s death.”
“All logical investigative steps have been concluded in this case,” Michael H. Schneider, the special agent in charge of the Denver field office, said in a statement. “The investigation did not identify any other individuals other than Brian Laundrie directly involved in the tragic death of Gabby Petito.”
Ms. Petito, 22, had been reported missing on Sept. 11, 2021, after she did not return from a monthslong cross-country trip with Mr. Laundrie, 23. The case gained national attention as many in the public scoured the couple’s photos and videos on Instagram and YouTube for clues.
Intense media coverage of the case also prompted criticism that it was an example of “missing white woman syndrome,” the disproportionate attention given to cases of missing white women compared with cases of missing people of color.
Mr. Laundrie returned home to his house in North Port, Fla., on Sept. 1 in the white Ford van that the couple had used for the trip, and that had been registered to Ms. Petito. On Sept. 17, Mr. Laundrie’s parents told the police that they had not seen Mr. Laundrie since Sept. 14.
Ms. Petito’s remains were found on Sept. 19 in the Spread Creek Dispersed Camping Area in Wyoming, where she and Mr. Laundrie had been seen together. The Teton County Coroner’s Office concluded that she had died of “blunt-force injuries to the head and neck, with manual strangulation,” the F.B.I. said.
On Oct. 20, Mr. Laundrie’s remains were found in the Myakkahatchee Creek Environmental Park in Sarasota County, Fla., the F.B.I. said.
A medical examiner concluded that he had died of a self-inflicted gunshot wound, the F.B.I. said. Near Mr. Laundrie’s remains, investigators found the notebook, a backpack and a revolver.
Richard B. Stafford, a lawyer for the Petito family, issued a statement thanking the F.B.I. and its victim services department for helping the family “navigate through the worst moments of their lives.”
“We truly appreciate the F.B.I.’s diligent and painstaking efforts in this extremely complicated case,” the statement said. “The quality and quantity of the facts and information collected by the F.B.I. leave no doubt” that Mr. Laundrie murdered Ms. Petito, he said.
Steven Bertolino, a lawyer for the Laundrie family, also released a statement on the closing of the case.
“Gabby and Brian are no longer with their families and this tragedy has caused enormous emotional pain and suffering to all who loved either or both of them,” the statement said, according to NBC News. “We can only hope that with today’s closure of the case each family can begin to heal and move forward and find peace in and with the memories of their children.”
Mr. Schneider thanked the public for providing thousands of tips.
“The F.B.I.’s primary focus throughout the investigation was to bring justice to Gabby and her family,” Mr. Schneider said. “The public’s role in helping us in this endeavor was invaluable as the investigation was covered in the media around the world.”