Brian Laundrie admitted he was responsible for Gabby Petito's death in his diary, according to the FBI

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Brian Laundrie left behind written evidence showing his "responsibility" for the death of his girlfriend, Gabby Petito, whose disappearance last year sparked a massive manhunt from Utah to Florida, the FBI announced Friday.

Federal investigators formally closed the investigation that led to the discovery of the body of Petito, a 22-year-old social media star, on September 19 in Wyoming.

Laundrie's body was found on October 20 in Florida.

Gabrielle Petito (left) and her fiancé, Brian Laundrie. Via Instagram

"All logical investigative steps have been brought to a conclusion in this case," FBI Special Agent in Charge of the Denver Office Michael Schneider wrote in a statement.

"The investigation has not identified any individual other than Brian Laundrie directly involved in the tragic death of Gabby Petito. The FBI's primary goal in its investigation was to bring justice to Gabby and her family," the statement added.

federal agency.

[Sister of Gabby Petito's boyfriend breaks the silence: "I want answers as much as anyone else"]

Laundrie's body was found in a nature reserve near her parents' home in Florida.

During a search of that area, a backpack, a notebook and a revolver belonging to Laundrie were also found.

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"A review of the notebook revealed written statements by Mr. Laundrie in which he takes responsibility for Petito's death," the FBI statement said.

A Florida medical examiner determined that Laundrie had died from a self-inflicted gunshot wound.

Petito died "strangled with her hands" at least three weeks before her remains were found in Wyoming, a medical examiner said.