Top prosecutor Andrew Weissmann, known as special counsel Robert Mueller’s “legal pitbull,” is reportedly leaving the Russia probe, signaling the two-plus year investigation into possible collusion between the Trump campaign and the Kremlin is drawing to a close.

Weissmann will both teach and study at New York University and undertake several public service projects, which include preventing wrongful convictions by boosting the court system’s forensic science standards, two unnamed sources told NPR.

Weissmann is credited for heading up the special counsel’s case against former Trump campaign chairman Paul Manafort, who faces seven and one-half years in prison after judges in Virginia and Washington, D.C. handed down sentences of 47 months and 43 months in jail, respectively.

As NPR reports, Weissmann’s departure from the Mueller probe is one of several in recent weeks:

His leaving will follow the departure of the senior-most FBI agent working on the Mueller probe, who has taken his own next step. Special Agent In Charge David Archey started a new job on March 4 as head of the FBI’s office in Richmond, Va. Earlier this month, another special counsel prosecutor, Brandon Van Grack, moved on to lead a Justice Department effort to enforce compliance with the Foreign Agents Registration Act, a law that has become the subject of intense interest following charges against Manafort, his right-hand-man Richard Gates, and former Trump national security adviser Michael Flynn.

Concerns over Weismann’s credibility as an independent investigator plagued the Mueller deputy since joining the Russia Probe. In December 2017, the Wall Street Journal reported that he attended former 2016 Democrat presidential nominee Hillary Clinton’s election-night party. Election filings also state that Weissmann donated several thousand dollars to the Democratic Party, including a $2,350 contribution to the Obama Victory Fund in 2008 and $2,000 to the DNC in 2006.

In July 2018, Weissmann came under scrutiny after Politico published details of two internal FBI reports that suggested that Associated Press reporters gave special counsel investigators information they had uncovered about Manafort during an off-the-record meeting in April 2017. According to the memos, the meeting was arranged by Weissmann to “obtain documents from the AP reporters that were related to their investigative reports on Paul Manafort.” Politico reported that the memos indicated that the four unnamed reporters disclosed to FBI agents the code to a storage unit Manafort kept in Alexandria, Virginia, telling them that they believed it possessed evidence regarding the former Trump campaign official’s business dealings in eastern Europe.