Former Trump campaign aide Sam Nunberg arrived at a federal court in Washington, D.C., on Friday to testify before a grand jury after threatening to ignore a subpoena from special counsel Robert MuellerRobert Swan MuellerSasse: US should applaud choice of Mueller to lead Russia probe MORE.

Nunberg arrived at the courthouse early Friday morning and used the public main entrance to enter the building, according to reports. Politico reports other witnesses, as well as Mueller’s investigators, have typically used nonpublic entrances to enter the courthouse.

When asked by reporters if he would speak following his testimony, Nunberg said “no,” according to Politico.

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Nunberg’s testimony comes after a bizarre series of television interviews on Monday in which he revealed he had been subpoenaed by Mueller’s investigators, who demanded he turn over correspondences with Trump and several other top campaign and White House officials.

"When I got the subpoena it was ridiculous to me. Why should I hand them over every email I’ve had with Steve BannonStephen (Steve) Kevin BannonFilmmaker behind Bannon doc says the movie a 'damning portrayal' Avoiding the tragedy of Brexit Bannon predicts 2019 will be 'most vitriolic year' in US politics 'since before the Civil War' MORE or Roger StoneRoger Jason StoneTrump: 'Haven't thought about' pardons for Mueller target Trump: Mueller acted honorably The Hill's Morning Report - Presented by Pass USMCA Coalition - Mueller report is huge win for President Trump MORE since November, since November of 2015?" Nunberg said during an interview on MSNBC.

The former Trump campaign aide also told The Washington Post that he was summoned to appear before the grand jury but planned to refuse.

“Let him arrest me,” Nunberg told the Post. “Mr. Mueller should understand I am not going in on Friday.”

During the interviews, he also predicted Mueller has evidence of criminal wrongdoing committed by Trump.

“I think he may have done something during the election,” Nunberg told NBC.

The White House denied those claims, calling them incorrect.

Nunberg abruptly reversed course in a Tuesday interview with The Associated Press, saying he would cooperate with Mueller after all.

"I’m going to end up cooperating with them," he said.

It was also reported on Tuesday that Nunberg told Fox Business Network's Charlie Gasparino that he intends to get treatment following the grand jury appearance.

When asked what specifically Nunberg would be treated for, Gasparino referred to a Monday report he provided on Fox Business.

"When I interviewed [Nunberg], and I interviewed him early, he admitted to me he was drinking," Gasparino reported.

"He’s also going to seek treatment for what ails him," he continued. "There’s something. Drinking I believe is a big part of it, and that’s what happened yesterday."

Nunberg worked as an aide early in Trump's presidential campaign until he was fired for allegedly breaching a confidentiality agreement and for revelations of racially charged social media posts he wrote in August 2015.