Former special counsel Robert Mueller, known for his investigation into links between Russia and President Trump’s 2016 campaign, was diagnosed with Parkinson’s disease four years ago, as confirmed by his family to The New York Times on Sunday.

“Bob was diagnosed with Parkinson’s disease in the summer of 2021,” the statement to the Times read.

According to the statement, “He stepped away from practicing law at the end of that year. He went on to teach at his alma mater’s law school during the fall semesters of both 2021 and 2022, and finally retired at the close of 2022. His family requests that their privacy be honored.”

A congressional committee had sought testimony from Mueller in its probe of the late financier and convicted sex offender Jeffrey Epstein.

In 2008, while serving as the FBI director, Mueller was involved when a 60-count indictment against Epstein was abandoned in favor of his guilty plea to two reduced state prostitution offenses. This agreement, often criticized, faced scrutiny after Epstein’s 2019 indictment for allegedly continuing to exploit underage girls after his brief imprisonment about a decade earlier.

The House Oversight Committee had announced plans to subpoena Mueller for testimony on a forthcoming Tuesday. However, the committee declared last week that it would rescind the subpoena, considering his health situation.

Individuals acquainted with Mueller’s condition informed the Times that the former FBI director has encountered speaking difficulties and mobility challenges in recent months.