The nation's first African American attorney general, Eric Holder, Jr., will announce his resignation on Thursday at 4:30 p.m. EST, according to USA Today.

After being nominated by President Barak Obama, Holder began serving as the 82nd Attorney General of the United States in February 2009. However, after five and a half years in office, inside sources confirmed that the 63-year-old former judge will step down, reports NPR. He plans to leave the Justice Department as soon as his successor is confirmed by Congress, which is a process that could last until 2015.

"Attorney General Holder has discussed his plans personally with the president on multiple occasions in recent months, and finalized those plans in an hour-long conversation with the president at the White House residence over Labor Day weekend," said an official to ABC News.

Sources say that Holder, one of the longest serving members of the Obama cabinet, has been increasingly "adamant" about leaving his post rather than serving for the rest of the president's second term.

During his announcement, the AG "plans to express his personal gratitude to the President for the opportunity to serve in his administration and to lead the Justice Department, which he will call the 'greatest honor of my professional life,'" the official added.

Holder's legacy will be marked by his record on fighting for civil, LGBT and voting rights. He also launched 20 investigations of abuses by local police departments and lobbied Congress to reduce prison sentences for non-violent drug offenders, which disproportionately hurts minorities.

Holder will also be remembered for being the only member of the cabinet to be held in contempt of Congress back in 2012 when the House Oversight and Government Reform Committee accused him of failing to release all of the documents relating to the Fast and Furious operation.

"There's no question that this is a -- it's a demanding job. But it is the honor of my professional life to serve the American people as attorney general," Holder said during an interview with ABC News earlier this year.