Republican Rep. Matt Gaetz is questioning whether federal prosecutors are applying a double standard by not bringing charges in connection with a graphic threat against him -- and suggesting his criticism of the Russia probe might even be a factor.

The conservative Florida congressman told Fox News’ Tucker Carlson on Tuesday that he received a threatening voicemail -- but the U.S. Attorney’s Office for the Northern District of California deemed the matter “a non-threat” and would not pursue a case. Carlson noted that the FBI had identified a suspect.

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“I just wonder, is it the fact that I’ve been a critic of some of the senior officials at the FBI that maybe leads to different treatment for the people who threaten me, as opposed to the people who actually get arrested who have threatened Eric Swalwell, you know, Ilhan Omar, Rashida Tlaib,” Gaetz said, referring to prominent Democrats. “Those people actually get arrested, whereas when people threaten conservatives, I hope there’s not a double standard.”

A spokesman for the U.S. Attorney's Office, though, pushed back on the suggestion that any official's politics would factor into a threat assessment.

"This Office prosecutes threat cases against public officials when law enforcement has determined there is a credible possibility that the threat could be carried out and the case otherwise meets our standards for prosecution. In assessing such threat cases, this Office does not take into consideration the politics of the public official who has been threatened," spokesman Abraham Simmons said in a statement. "This Office prosecutes threat cases without discrimination on the basis of the public official’s viewpoint or any other impermissible basis."

Gaetz later responded with a string of tweets which read, in part: "The US atty shares a deeply flawed read of the criminal code. It is not the *ability* to murder a federal official, linked to a threat, that creates culpability. It is the threat itself. The speaker needs merely to intend to make the threat (not commit the murder) to be culpable."

He added, "Under the US atty’s incorrect read of the law, every death threat 2 every federal official is legal - no matter the words used. Just so long as the FBI doesn’t think you *really* mean it. This jerk called my office three times. He threatened to come after my family."

The FBI did not respond to a request for comment.

Gaetz, speaking with Fox News, shared a recording of the threat, in which a male voice can be heard saying, “Gaetz, you pathetic piece of s---. Do you know that I could blow your f---ing head clean off your shoulders from over a mile away. Watch your back, b----. You pathetic little piece of s---. You got your head so far up Trump’s ass, I could still take it off your shoulders. F--- you Gaetz. I’m coming after you, b----.”

Late last week, Gaetz said, he was told that the U.S. attorney “made the determination that this was a closed matter, that they would bring no charges, and that we’re just supposed to deal with that.”

According to Gaetz, this was not the only threat he has received, and other messages mentioned his family. He claims this happened after he was the target of a physical attack at a political event.

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"Look, it’s been a crazy few weeks for me, I mean, just a few weeks ago I had a member of Antifa, a stated member of Antifa, assault me at a town hall meeting and get arrested,” he said.

Gaetz said support from his Democratic colleagues has been sparse. He said that while Rep. Stephanie Murphy, D-Fla., condemned the attack against him, a staff member for 2020 hopeful Pete Buttigieg encouraged people to throw urine on him (the staffer later apologized).

“I wish there would be more bipartisan support for non-violence,” Gaetz said.

Gaetz himself is under investigation by the House Ethics Committee for a tweet he directed at President Trump's former lawyer Michael Cohen before Cohen was set to appear before Congress.

"Hey, Michael Cohen, do your wife and father-in-law know about your girlfriends? Maybe tonight would be a good night for a chat. I wonder if she'll remain faithful when you are in prison. She's about to learn a lot," Gaetz tweeted.

Gaetz has since apologized to Cohen and publicly stated that he should not have said anything about his family.

Fox News' Alex Pfeiffer contributed to this report.