Former Secretary of State Rex Tillerson was spotted entering a congressional office building on Tuesday morning for what a committee aide told The Daily Beast was a meeting with the leaders of the House Foreign Affairs committee and relevant staff about his time working in the Trump administration.

Tillerson’s appearance took place as virtually every other Trumpworld luminary has been stonewalling congressional oversight efforts. At the same time that the former Secretary of State was speaking before lawmakers, former White House counsel Don McGahn was ignoring a subpoena to testify in front of the House Judiciary Committee.

Tillerson’s arrival at the Capitol was handled with extreme secrecy. No media advisories or press releases were sent out announcing his appearance. And he took a little noticed route into the building in order to avoid being seen by members of the media.

Tillerson had a notoriously prickly relationship with the president, reportedly calling him a “moron” in private. But he was present during critical moments of the administration, including Trump’s 2017 private meeting with Russian President Vladimir Putin in Hamburg, Germany.

Since leaving his post, he has rarely made public appearances, save for speaking at a panel in Houston in December. During that appearance, he said there was “no question” Russia interfered in the 2016 presidential election.

"So often the president would say, here's what I want to do and here's how I want to do it, and I would have to say to him, Mr. President, I understand what you want to do but you can't do it that way. It violates the law," Tillerson said.

Tillerson’s interview by House Foreign Affairs Committee Chairman Eliot Engel (D-NY) and ranking member Michael McCaul (R-TX)  comes a month after Special Counsel Robert Mueller published his report on Russian interference in the 2016 presidential election. Since then, top Democrats on the Hill have demanded that Attorney General Bill Barr and Mueller answer questions related to the report and its publication. Barr has declined to testify before the House, citing the insistence of the committee that staff lawyers be allowed to conduct some of the questioning. Mueller is reportedly in negotiations to testify, though the Department of Justice had previously not agreed on a date for him to do so.

On Tuesday, CNN reported that Mueller’s team had expressed reluctance about the possibility of a testimony taking place in public for fear that it would appear political.