David Charles Hahn, who was nicknamed the “Radioactive Boy Scout,” received regular visits from the FBI for nearly a decade from 2005 through 2015, Ars has learned.

Hahn, who was profiled by Harper’s Magazine in 1998 for his attempts to build a homemade breeder nuclear reactor in his mother’s backyard shed, passed away late last year in Michigan at the age of 39. Last month, Ars reported that Hahn did not die as a result of radiation poisoning.

Upon his death, we filed numerous Freedom of Information Act requests with various federal agencies, including the FBI. Amongst the documents we received were three FBI reports dating between 2007 and 2010. They detail three separate instances when people reported to law enforcement that they believed that Hahn may be trying to restart his nuclear activities. When local and federal authorities investigated, they found no such evidence.

With these reports, Ars contacted Kenneth Hahn, David’s father. He said he had never seen these documents before.

However, the elder Hahn told Ars that, upon his son’s return from military service in 2005, David would receive regular, unannounced visits from the FBI at least annually. The FBI would interview David and search for any evidence of nuclear material.

“Each time they were really hoping to find something,” Kenneth Hahn told Ars, adding that the searches took two to three hours.

When the FBI would turn up, Kenneth would drive over to his son’s house, just a half-mile away, and sit in his own car and watch. Kenneth said that the FBI team was always professional, but he felt frustrated by the frequency with which these searches happened. He was also frustrated that the federal agents frequently brought numerous law enforcement cars and search dogs with them.

“That would drive you nuts, wouldn’t it?” he said.

Kenneth Hahn said that the teams were always lead by Mark Davidson, a special agent with the FBI based in Detroit. Ars reached Davidson, who declined to comment, and referred us to the FBI’s press office in Washington, DC.

“The FOIA documents speak for themselves and we do not have an additional comment to provide,” a spokesman e-mailed.

“Does not possess any nuclear materials”

The earliest of the documents date back to April 23, 2007. That’s when someone (the name is redacted) reported to the FBI in Toledo, Ohio, that Hahn was mentally unstable and was again attempting to build a nuclear device. According the report , the person told the FBI that Hahn was “using cocaine heavily and is not taking his prescribed medication for a mental illness.”

That same day, someone (again redacted) also walked into the sheriff’s office in Montgomery County, Texas, to make a similar allegation about Hahn and his purported attempts to restart his experiments. That report specifically said that Hahn kept a “small nuclear reactor” in his freezer. The witness described the reactor as the “size of a basketball.” The next day, law enforcement went to Hahn’s apartment to run radiological tests, but found nothing.

The FBI reached Hahn by phone—he was out of town—and he told them that he “does not possess any nuclear materials and does not intend to acquire any nuclear materials.”

Similarly, a 2010 FBI report indicates that a Shelby Township police detective believed that Hahn was again trying to conduct nuclear experiments. No such evidence was ever found.

When Ars sent these reports to Kenneth Hahn, he said that he believed that they were made by former shipmates and friends of his son’s, who served with him aboard the USS Enterprise. Kenneth believed that those friends were “trying to get him help” by reporting him to the authorities. However, Kenneth added, he has no idea why they would believe that David would have nuclear material.

“He was very sensitive person,” Kenneth Hahn continued. “He was very smart. He wasn’t doing anything to hurt anybody else. Dave worked hard at anything he had to do. He achieved a lot in a short time in his life. Dave wasn’t mean to people.”