Brian Laundrie died from a self-inflicted gunshot wound to the head, his family's lawyer has confirmed.
According to The New York Post, a forensic anthropologist determined the cause of death to be suicide.
Attorney Steve Bertolino told the outlet: "Chris and Roberta Laundrie have been informed that the cause of death was a gunshot wound to the head and the manner of death was suicide.
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"Chris and Roberta are still mourning the loss of their son and are hopeful that these findings bring closure to both families."
Laundrie had been a 'person of interest' in the disappearance and death of his late partner Gabby Petito.
He told his parents he was going on a solo hike around the Carlton Reserve, before also disappearing completely - sparking one of the most well-publicised manhunts in recent US history.
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Last month, the FBI confirmed that human remains found in Florida belonged to Laundrie, saying in a statement: "A comparison of dental records confirmed that the human remains found at the T. Mabry Carlton, Jr. Memorial Reserve and Myakkahatchee Creek Environmental Park are those of Brian Laundrie."
Bertolino told Fox News at the time: "Chris and Roberta Laundrie have been informed that the remains found yesterday in the reserve are indeed Brian's.
"We have no further comment at this time and we ask you to respect the Laundrie family's privacy at this time."
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Police said Laundrie's remains were submerged in the marshy park for weeks before they were found, which proved to be a challenge for coroners.
Authorities have also been trying to repair a personal notebook retrieved from a dry bag found near his body as part of their investigation into the death of Petito.
Both the Myakkahatchee Creek Environmental Park and Carlton Reserve are a short drive from Laundrie's family home.
Previously, Laundrie and Petito had been travelling the national parks of the USA together, but Petito was reported missing and her body was later discovered in Grand Teton National Park in Wyoming.
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The coroner revealed that her death was a homicide, and that she was killed by strangulation.