Brian Laundrie scrawled messages in a notebook admitting that he killed his girlfriend Gabby Petito, the FBI said in a statement Friday as they announced that their investigation into the couple’s deaths was now closed.

The notebook was found alongside Laundrie’s remains in a wooded area in Florida in October, weeks after police say he killed Petito while they were traveling the country in a van.

“The FBI’s primary focus throughout the investigation was to bring justice to Gabby and her family,” said FBI Denver Special Agent Michael Schneider. “The public’s role in helping us in this endeavor was invaluable as the investigation was covered in media around the world.”

The influencer couple documented their “van life” trip in cheery posts on YouTube and Instagram. But, beneath the service, they’d had explosive arguments, including one that prompted witnesses to call police in Moab, Utah.

Petito’s parents reported her missing on Sept. 12 after Laundrie returned home alone to Florida and refused to tell anyone where Petito was. The FBI said text messages were sent between Laundrie and Petito’s phones after she was killed, indicating Laundrie tried to obstruct her death and act like she was alive. He also continued using Petito’s debit cards.

As the case made headlines around the world, and police scoured the country for any sign of Petito, Laundrie vanished while purportedly going on a hike near his parents’ North Port home.

Petito’s remains were found on Sept. 19 at a Wyoming campsite near the couple’s last known shared location, and a coroner determined she died of “blunt-force injuries to the head and neck, with manual strangulation.” The manhunt for Laundrie went on for weeks, with his parents joining in searches of the Myakkahatchee Creek Environmental Park, a park he frequented.

Laundrie’s remains—along with the notebook, a backpack, and a revolver—were eventually found on Oct. 20 after his parents decided to search the park again with law enforcement. The area had been flooded during earlier searches, the FBI said. A medical examiner concluded in November that Laundrie died by suicide from a self-inflicted gunshot wound.

“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,” Schneider said in the statement.