Police in Minnesota, however, discovered what appeared to be a suicide note after Smith was found at a hotel near the Mayo Clinic on May 14, the Chicago Tribune reported Thursday.
The GOP operative who was searching for the 33,000 emails missing from Democrat Hillary Clinton's private server allegedly committed suicide by pumping helium into a plastic bag over his head, according to police.
The Tribune reports that Smith had a "carefully prepared file of documents" next to him, including a suicide note.
No information was given about the 81-year-old's death in his obituary, and the coroner in Lake County, Minn., where he lived, told the Daily News at the time that it uncharacteristically did not have records about his death.
His official cause of death was listed as "asphyxiation due to displacement of oxygen in confined space with helium".
The cause of Smith's death had previously been a mystery, though it was widely assumed he had died of natural causes.
"When I got there and saw the tank, I thought, "I've seen this before", and was able to put two and two together", the former employee told the Tribune.
Smith's body was cremated, according to the Tribune.
Details about Smith's unidentified illness were not immediately available, and the Mayo Clinic was barred from sharing whether he was a patient there.
Flynn, who was sacked in February just weeks after starting in his role as national security adviser to Trump and making misleading comments about his conversations with Russia's US ambassador, has not commented on Smith's search for Clinton's e-mails, or any involvement Flynn himself may have had with Smith in the process. However, Smith never confirmed to the Journal whether or not he was indeed working alongside Flynn.
Smith's account is consistent with the findings from United States investigators examining Russia's involvement in the 2016 U.S. presidential election, according to sources cited by The Journal.
A later report in the Journal claimed Smith also referenced White House aides Kellyanne Conway and Steve Bannon and campaign policy adviser Sam Clovis in a recruitment document for his attempts to track down the emails.