A Massachusetts man was arrested last week after authorities said he sent FBI Director Kash Patel's girlfriend an email saying he would be "happy" when her face is "canoed by an assault rifle," court records unsealed on Thursday showed.

Alden Welch Ruml, 26, was arrested on Friday and charged by federal prosecutors in Boston with making threats in interstate commerce. Authorities said he sent the threatening email upon becoming upset about a news article concerning Alexis Wilkins, Patel's girlfriend.

That February 28 article described the use of FBI resources to provide security to Wilkins, a country music singer, as well as conservative political views of Patel and Wilkins and their association with the Make America Great Again political movement, a newly unsealed search warrant application said.

"Watch your back," the profane email said, according to the affidavit.

Ruml pleaded not guilty during a court hearing on Friday following his arrest. He faces a maximum sentence of five years in prison if convicted.

William Fick, a defense lawyer, declined to comment. The FBI did not respond to a request for comment.

Wilkins was not initially identified as the alleged victim in the case. The indictment against Ruml instead described her only as an unnamed individual who had a personal relationship with a "high-ranking employee in the United States government."

According to court papers, she had been in Arizona when she received the email. She indicated being "frightened by the threatening email and changing their upcoming travel arrangements as a result," an FBI agent said in the affidavit.

Law enforcement determined it was sent by Ruml, who told agents who interviewed him at his place of work in Cambridge, Massachusetts that he had been "upset" by the news article, the affidavit said. He denied any intent to harm anyone.