Washington — A Virginia man admitted that while he was employed by the Department of Homeland Security, he and his wife wrote a letter on fake State Department letterhead and impersonated an official in order to threaten a French couple who had employed their daughter as an au pair in Southern France. 

In court on Monday, Ralph Karau pleaded guilty to one count of Misuse of Names, Words, Emblems, or Insignia — a law that makes it illegal to fraudulently use official U.S. government symbols “for the purpose of conveying the false impression that such communication is from a department,” according to court documents.  

According to records filed with the plea agreement, in October of 2019, Karau and his wife, Kathleen, prepared the letter soon after their daughter had returned to the U.S. from her stint as an au pair, and a forensic investigation showed that Karau had worked on the letter on devices issued to him by the government.

“The defendant’s daughter alleged that she was mistreated by the Madiot family,” court documents explained, without detailing the allegations of mistreatment. 

“After hearing of these complaints from their daughter, the defendant and his wife together created a fraudulent letter to send to the Madiots,” the filing said.

The counterfeit correspondence falsely informed the French couple that a “formal complaint” had been filed against them with the State Department for their alleged mistreatment, and it warned that they could be denied entry into the U.S. because of the claim. 

Further, “[t]he letter implied that a ‘financial settlement’ paid to the Karau’s daughter would be in the best interest of the Madiots,” the filings reveal. 

The Karaus invented a State Department official, “Karl Wilkinson, Deputy Chief, International Investigations Unit” and used the official seal of the State Department to give the letter an air of legitimacy. 

Karau, who at the time worked as a senior adviser to the director of real property at DHS, also admitted he had sent the letter through a post office in Washington, D.C., so that it would be postmarked in the nation’s capital, according to the Statement of Offense filed in the case. 

Because of his employment at DHS, Karau had a top-secret security clearance, the court records also noted. 

CBS News has reached out to DHS for comment on the case and clarification about Karau’s employment status at the department. 

Upon their receipt of the note, the French couple was described as “deeply concerned for any legal or other consequences they might face,” and contacted the French Embassy in Washington, D.C., which brought the issue to the U.S. Embassy in Paris.

A spokesperson for the U.S. State Department referred CBS News to the U.S. attorney’s office in Washington, D.C., which prosecuted the case. Court records filed by the prosecutors explained, “The U.S. Department of State did not know of this fraudulent letter and did not authorize its drafting or the use of its official seal in the letter.”

The issue was ultimately referred to U.S. law enforcement, resulting in charges against the Karaus. 

Kathleen Karau entered into a Deferred Prosecution Agreement with the government, in which she accepted responsibility for her conduct without being formally convicted. Her attorneys declined to comment on this story.

Ralph Karau now faces a maximum sentence of one year in prison and a $100,000 fine. His legal team did not immediately return CBS News’ request for comment.

Nicole Sganga and Paulina Smolinski contributed to this report.