A man walked into a Weymouth post office in March of last year and applied for a passport. The only problem is, the feds say, that man died in Boston 22 years ago.

The Quincy man, “whose true identity is unknown” and is referred to by federal law enforcement officials only as “John Doe,” was arrested Thursday and charged with one count of false statement in a passport application and one count of aggravated identity theft. The man appeared briefly in federal court in Boston the same day, where he was ordered detained ahead of a hearing scheduled for Wednesday at 2 p.m.

The man had been getting away with the alleged identity theft, too, until it came to those meddling feds. The alleged scheme had been successful for years until he applied for the passport and a U.S. Department of State fraud investigation commenced.

The DOS agent who investigated the case wrote in her affidavit supporting the criminal charges that Doe had successfully used the identity of the deceased, who she identifies by the initials H.H., to obtain a Massachusetts driver’s license — issued in 2018, 2019 and last year — a birth certificate and a Social Security card.

With the basics out of the way, the feds say Doe used H.H.’s identity to obtain an EMT-Basic certification in 2021 and upgraded to a EMT-Paramedic certification last year. He then went on to allegedly attend the Massachusetts Firefighting Academy, from which he graduated in January. He used these to become a firefighter with the Melrose Fire Department, where he had been employed since Jan. 23.

But the feds say H.H. — who was born in 1989 and died in 2002 — wasn’t enough of an identity for Doe, so he took on a second identity: Truong Nguyen, a lawful permanent resident since moving from Vietnam at around four years old in 1979 and who was ordered deported from the United States following a conviction for second-degree burglary in late 1991.

But, in a twist, this second identity — which a fraud investigation performed by the state Registry of Motor Vehicles in 2018 had determined was the alias of H.H. — may actually be the real one.

“Based on the investigation, I believe NGUYEN is an alias of HH and may be the possible true identity of DOE, the individual who has assumed the identity of HH,” DOS Agent Rachel Malcolm wrote in the affidavit.

Malcolm wrote that Nguyen was actually never physically deported back to Vietnam and, in addition to the earlier criminal history, was arrested in 2010 for embezzlement and larceny in a scheme to allegedly steal $46,000 from the Norwell Firefighters Union while serving in it as an officer.