Antonin Dehays during a PBS NewsHour story on teachers and students retracing the lives of those who died at Normandy.

For two years, the historian had been visiting a National Archives facility in Maryland to review files on U.S. pilots who had crashed in German-controlled Europe during World War II.

Last week, Antonin Dehays, a 32-year-old Frenchman, finally acknowledged one reason why, federal investigators say: He’d been stealing the dog tags of dead American heroes, selling many of them on eBay.

“The theft of our history should anger any citizen,” the Archivist of the United States David Ferriero said Tuesday in a statement, “but as a veteran I am shocked at allegations that a historian would show such disregard for records and artifacts documenting those captured or killed in World War II.”

If convicted, prosecutors say, Dehays could face up to a decade in prison. In 2005, a Virginia man was sentenced to two years for stealing dozens of Civil War-era documents, including letters by Jefferson Davis and Robert E. Lee, from the National Archives. And five years ago, an Archives official admitted to stealing nearly 1,000 recordings, many of them rare.

See Dehays in a PBS NewsHour segment on Normandy

Though Archive staff didn’t realize any of the World War II tags had been stolen until this year, investigators allege that Dehays’s scheme dates back to the fall of 2015, when he twice visited the National Archives at College Park to view the file of Henry W. Davis, a U.S. airman downed in the war.

Special Agent David Berry of the Office of Inspector General later discovered an article, written in French, that featured a photograph of Dehays and an excerpt from his book, “Sainte-Mere-Eglise: An American Sanctuary in Normandy 1944-1948.”

It also included a picture of Davis’s dog tag, which appeared to be identical with one the Archives had also photographed, the complaint said. Same dent near the necklace hole. Same dirt smudge in the lower-right corner.

The article, though, said that the dog tag belonged to a “collection privée” — a private collection.

In December 2016, Dehays perused the file of Leonard R. Willette, whose story was special both because he flew for the legendary Tuskegee Airmen and because one of his dog tags was brass, which is quite rare.

Then, in the spring 2017 issue of the Military Aviation Museum’s newsletter, Dehays appeared in a story alongside Willette.

The piece told the pilot’s story, explaining that he had passed up a chance to attend West Point because he didn’t want to wait any longer to join the war effort. On Sept. 22, 1944, he was escorting bombers in a P-51 over Germany when his engine lost oil pressure and he crashed. He was buried that same day, and not long after, his mother received a personal telegram from Eleanor Roosevelt, who had written to express her sympathy.

Dehays, the article said, donated Willette’s dog tag but asked for a favor in exchange: to sit in a Spitfire airplane, “one of Antonin’s ‘bucket list’ dreams come true.”

Above the story are photos of Willette and his dog tag, and next to those is one of Dehays, grinning in the cockpit of the fighter.

Dehays returned to the National Archives facility at least once more, on May 12, 2017. He asked to see box 352, which he looked through for 24 minutes and left.

Two weeks later, a staff member discovered that about 30 dog tags that had been in box 352 were now missing.

On Friday, the complaint alleges, law enforcement officials executed a search warrant at Dehays’s home in College Park, Md., where they discovered six dog tags and related documents that belonged to the archives.

Dehays, authorities say, admitted that he’d stolen the historic artifacts for “private financial gain” and that he sold them on eBay.

Dehays, who did not respond to a request for comment, had been working as a researcher for National History Day, a nonprofit education organization, until his home was raided last week. A spokesman at the nonprofit said Dehays had been terminated but wouldn’t elaborate.

His LinkedIn page says he earned both a master’s degree and a doctorate from universities in France.

Dehays’s Facebook page is littered with photos of vintage military planes and fawning references to service members who fought in World War II.

On Jan. 26, he posted five photos of his visit to a favorite local spot, along with this message: “A day spent at the National Archives is always a good day.”