Attorney General Eric Holder testifies on Capitol Hill in Washington, Tuesday, April 8, 2014, before the House Judiciary Committee hearing on the oversight of the Justice Department. (AP Photo/Manuel Balce Ceneta)

U.S. Attorney General Eric Holder will announce his resignation on Thursday after heading the Justice Department for six years, according to the White House.

Citing two sources “familiar with the situation,” NPR first reported that Holder will exit the U.S. Department of Justice as soon as his replacement is confirmed, though the process could potentially drag out into 2015.

The White House told the Associated Press that President Barack Obama will announce Holder’s departure later Thursday. Holder is the first black attorney general, and his tenure is the fourth longest on the job.

But Holder has faced plenty of controversy during his tenure as the nation’s top law enforcement officer. Holder, 63, faced harsh criticism for his involvement in the Fast and Furious gun-walking scandal, an operation that allowed thousands of guns — which were ultimately lost and fell into the hands of Mexican drug cartels — to cross into Mexico.

Congress later voted to hold Holder in contempt over his withholding of Fast and Furious documents.

The DOJ also came under fire over its probe of classified leaks. The department investigated Fox News reporter James Rosen, naming him a “co-conspirator” for reporting based on the account of a government source.

Holder, one of the longest serving members of the Obama administration, has reportedly been “adamant” about leaving the Justice Department before the end of President Barack Obama’s second term.

More from the NPR report:

Holder most wants to be remembered for his record on civil rights: refusing to defend a law that defined marriage as between one man and one woman; suing North Carolina and Texas over voting restrictions that disproportionately affect minorities and the elderly; launching 20 investigations of abuses by local police departments; and using his bully pulpit to lobby Congress to reduce prison sentences for non-violent drug crimes. Many of those sentences disproportionately hurt minority communities.

And then, there’s his relationship with Congress. From the day Holder’s nomination was announced, Republicans led by Sen. Mitch McConnell, R-Ky., signaled he would be a political lightning rod.

The attorney general’s portfolio, which spans sensitive law enforcement cases and hot button social issues including marijuana and gay marriage, didn’t help. But even longtime aides say Holder didn’t do enough to help himself by shrugging off preparations and moot sessions before congressional appearances and speaking off the cuff — and obliquely.

Holder reportedly informed his DOJ staff at some members of Congress on Thursday morning about his decision to resign. He has not revealed what his future plans hold.

Solicitor General Don Verrilli is believed to be a leading candidate to succeed Holder as attorney general.