Andrew McCabe was named acting director of the FBI after the sudden firing of Director James Comey by President Donald Trump on Tuesday. He’s also under investigation for his role in Hilary Clinton’s private email server scandal.

McCabe will be tasked with looking into potential Russian interference in the U.S. election until the White House names an interim director for the agency. That decision could come sometime this week, ABC News reported Wednesday.

McCabe has been with the FBI for 20 years, and was promoted last year to deputy director, the FBI’s second highest position. He started with the agency in 1996 focusing on New York’s organized crime, and in 2006 shifted to tackling domestic terrorism, according to NBC News.

In an interview with the Los Angeles Times last year, McCabe said terrorism was his number one priority.

“That is the scariest thing for me right now,” McCabe told the publication. “It’s the broadening and intensity of the terrorism threat, the crowd-sourcing of terrorism, the flood of propaganda, the enormous number of folks who have become swept up in that propaganda.”

As part of his job at the FBI, McCabe took part in the investigation into former Secretary of State Hillary Clinton’s use of a private email server. But while running for state Senate in 2015, McCabe’s wife received funds from Clinton ally and Virginia Gov. Terry McAuliffe’s political action committee, Business Insider reports. McCabe alerted a department ethics official about the donation.

Now, the Department of Justice is looking into how the FBI handled the Clinton emails. As part of its probe, the DOJ will review “allegations that the FBI deputy director should have been recused from participating in certain investigative matters.”

Sen. Chuck Grassley (R-Iowa) told CNN Wednesday he has concerns over McCabe taking the top job at the FBI.

“He’s got political problems because of McAuliffe helping his wife and I don’t think he’s the person that should be taking over,” he said.

Attorney General Jeff Sessions and Deputy Attorney General Rod Rosenstein are interviewing four to eight individuals for the job, Justice Department officials told CNN.