Former Sheriff David Clarke abused his authority when he ordered the mistreatment and intimidation of a fellow passenger on a flight to Milwaukee in January, according to a newly revealed FBI search warrant affidavit, because Clarke assumed the man was showing disrespect toward the right-wing Donald Trump booster.

The affidavit, which had requested a search of Clarke’s private email account, was revealed as part of a filing in U.S. District Court in Wisconsin on Thursday. It’s unclear if it indicates continued interest by the FBI or just details information from months earlier.

In May, federal prosecutors informed Clarke’s attorney that they weren’t going to pursue charges against him over his encounter with passenger Dan Black. But according to the affidavit, filed in March, investigators for the Audit Services Division of the Milwaukee County controller’s office determined as part of its own investigation that Clarke had “used his official position as sheriff of Milwaukee County in excess of his lawful authority to direct his deputies to stop and question Black without legal justification.”

The unsealed affidavit was first spotted in the new federal court filing by a Detroit Free Press reporter.

SCOOP: FBI investigating former Milwaukee County Sheriff David Clarke, a Donald Trump surrogate, according to search warrant affidavit I just stumbled upon. Heads up @journalsentinel @realDonaldTrump pic.twitter.com/13nZkpA6TW — Robert Snell (@robertsnellnews) December 29, 2017

According to the affidavit, Black told Milwaukee investigators that he spotted Clarke after the men boarded the Milwaukee-bound plane in Dallas on Jan. 15. When he asked Clarke if he was, in fact, the sheriff, and Clarke confirmed it, Black said he shook his head. When Clarke asked him if he had a “problem” with that, Black said he didn’t respond because he didn’t want to get in trouble. Investigators found Black’s account credible, according to the affidavit.

Clarke texted one of his officers to detain Black upon arrival in Wisconsin, according to the affidavit. “Just a field interview, no arrest unless he becomes an asshole with your guys,” Clarke texted, according to a screenshot obtained of the texts. “Question for him is why he said anything to me. Why didn’t he just keep his mouth shut?”

Black was then met by six deputies and two police dogs, according to a complaint he filed against Clarke with the Milwaukee County Executive’s Office. Black was detained and questioned by deputies about “remarks” he had made to Clarke, which Black denied, and then was escorted to a friend’s car to leave the airport.

The affidavit was filed by FBI special agent Jennifer Walkowski, who initially asked that it be sealed, to obtain a search warrant to access Clarke’s emails through Google. It accuses Clarke of using his email account to encourage his staff to attack Black online in posts on the official Facebook page for the Milwaukee County Sheriff’s Office.

One post included Black’s complaint with the comment: “Next time he or anyone else pulls this stunt on a plane they may get knocked out.” Such messages, including one calling Black a “snowflake,” were likely either written by Clarke or “he directed his staff to post the messages for him,” states the affidavit.

The search warrant was granted, and the filing Thursday listed an inventory of requested email records and related information held by Google.

Despite the damaging information in the affidavit, the Department of Justice sent a letter to Clarke’s attorney in May saying that a decision had been made “not to criminally prosecute any civil rights offenses” against Clarke because of concerns that such a case would be difficult to prove “beyond a reasonable doubt.” The letter warns, however, that the “decision could change if additional information came to light.”

Black still has a civil rights lawsuit pending against Clarke.

Clarke said Friday in an email response about the affidavit to Law & Crime: “I am NOT currently under investigation by the FBI in the Black case. That investigation was closed back in May 2017.” He attached the letter from the Justice Department. “You’ll have to ask FBI why the return of the search warrant took so long.” He said he was notified by Google that the search warrant request was made in March.

Later he blasted the “liberal media” in a tweet for reporting the unsealed details of the affidavit, calling it a “hit job.”

Lib media did a drive-by hit job on me today with a FAKE NEWS STORY that I am under investigation by the FBI. It’s a LIE. Last MAY the US Atty’s office found NO EVIDENCE of wrongdoing for doing police work. Lying Lib media took a story from LAST MAY & reports this today as new. pic.twitter.com/ijyWp1IEW5 — David A. Clarke, Jr. (@SheriffClarke) December 30, 2017

Clarke resigned as sheriff in August in the wake of concerns about troubling deaths in his county jails. Clarke, who spoke at the Republican National Convention, infamously encouraged Trump supporters to take up “pitchforks and torches” because the system was “rigged” against Trump. He has also called members of the Black Lives Matter movement “creeps.” In June he said he withdrew his acceptance of a job offer as assistant secretary of the Department of Homeland Security to continue to work on Trump’s behalf in other ways.