On Thursday, as leaked secrets about U.S. drone warfare attracted global news coverage, LanAnn Bryant was warned the Islamic State group may have her personal information and she should be on the lookout for anything suspicious.

The public school teacher’s son Brandon – a former drone operator turned whistleblower – was in Germany to testify before a parliamentary committee, and she became suspicious as two men from the Air Force's investigative arm warned her about the jihadi group.

She was told not to share their vague warning with anyone outside her family, including her Montana school’s leaders, she told her son’s lawyer Jesselyn Radack in an email, leaving her uneasy about the authorities' true motivation for the visit.

Radack, whose high-profile clients include National Security Agency whistleblowers Edward Snowden and Thomas Drake, says she believes the in-person warning was a blatant attempt at whistleblower intimidation.

In fact, Radack says, it’s not the first time authorities have given such a notice to her drone whistleblower clients. In late March, she says, the stepparent of another client, who she declined to publicly identify, was given a similar warning, as was Brandon Bryant himself.

The stepparent, like LanAnn Bryant, was contacted by the Air Force Office of Special Investigations, Radack says. Brandon Bryant, a Predator drone operator who left the Air Force in 2011 and subsequently slammed the program's leaders for the amount of collateral damage they impose, was contacted by the FBI.

“This is the U.S. government wasting taxpayer dollars trying to silence, intimidate and shut up people,” Radack says. “It’s a very amateurish way to shut up a whistleblower: by intimidating and scaring their parents. This would be laughable if it wasn’t so frightening.”

“It’s no coincidence at all that this happened on the same day as The Intercept’s series on the ‘drone papers’ and on the same day Brandon was testifying before the Bundestag,” she says of the most recent visit.

The Intercept's reporting on drones last week showed a high number of civilian casualties from U.S. airstrikes. The website did not identify the source of classified documents it published and no whistleblower has publicly claimed credit.

Radack might be right that the timing of the warning LanAnn Bryant received was no coincidence, a spokeswoman for the Air Force Office of Special Investigations says.

But the spokeswoman insists the warnings are not being cooked up to spook dissidents.

“[T]his had absolutely NOTHING to do with whistleblower intimidation!!!” the spokeswoman, Linda Card, said in an email.

Card says the FBI compiles lists of people who apparently are being researched by Islamic State terrorists and then sends lists of Air Force-affiliated subjects to the Office of Special Investigations so the individuals can be notified.

It’s unclear how the the FBI prepares the lists it provides to federal organizations like the Air Force.

The Air Force received sizable lists of people from the FBI in March and July, Card says, perhaps related to information hacked from the Office of Personnel Management. Card was unable to say how many people received warnings pursuant to FBI listing.

People who are on the lists are told to be on alert and are given a standard brochure, she says. Being warned doesn't mean there's a credible threat, she says, adding it would make sense that people with high public profiles and their families would be researched by terrorists.

“When you start talking leaked documents and security interests and drones in the same sentence, you’re going to raise ISIS’s interest,” Card says. “He’s in the news. If he hadn’t done that and got in the news, she probably never would have gotten on a list.”

She says “this investigation was to protect her, to let her know her son was treading on some dangerous ground and it’s gotten ISIS's interest and she needs to be aware of her surroundings, that’s it.”

Radack says she's unconvinced by the Air Force's explanation for the in-person warnings given to her clients' parents.

“The Air Force Office of Special Investigations is going out of its way to tell whistleblowers that the 'consequences' of exercising their First Amendment rights by speaking to the press will be that they and their families will end up on terrorist hit lists,” Radack says.

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“The message is clear: ‘To keep your family safe from ISIS, stop talking to the press.’ It doesn’t get much more intimidating and chilling than that.”

Michael Crunk, an Air Force Office of Special Investigations employee who left his business card with LanAnn Bryant, says he’s not authorized to comment on the warning he conveyed.

A Montana FBI agent declined to confirm she provided Brandon Bryant a warning in March or comment on other warnings related to the Iraq- and Syria-based jihadi group. Spokespeople for the FBI’s Salt Lake City field office did not respond to a request for comment.

Brandon Bryant said in a statement he hopes for public support in his criticism of U.S. drone policies and that those who are unwilling to support him should "leave myself and those that I love alone."