Zane David Memeger - who as the region's U.S. attorney oversaw successful prosecutions of U.S. Rep. Chaka Fattah, Colleen "Jihad Jane" LaRose, and members of Ironworkers Local 401 - announced his resignation Tuesday after nearly seven years in the position.

In a statement, Memeger, 52, of Swarthmore, called serving in the role the highest honor and most fulfilling duty of his legal career. He said he plans to leave on Dec. 23.

His first assistant, Louis D. Lappen, will lead the office of 235 federal prosecutors and support staff until the administration of President-elect Donald Trump names a new nominee.

"The time has come for me to step away to focus on my family and explore new opportunities in the private sector," Memeger said in the statement.

Lappen, who has worked for the Justice Department since 1997, lauded his boss' tenure.

"He's a highly intelligent, talented, and incredibly dedicated public servant," he said. "It's my role to keep the work Zane presided over going forward."

The U.S. Attorney's Office for the Eastern District of Pennsylvania, working with federal agencies including the FBI, the IRS, and the Drug Enforcement Administration, has broad investigative and prosecutorial powers in Philadelphia and eight surrounding counties.

President Obama nominated Memeger, a native of New Castle County, Del., and a former mob prosecutor, as the region's top federal prosecutor in 2010, following the resignation of Patrick Meehan, who filled the role during George W. Bush's presidency and left to launch his career in Congress.

Under Memeger, the Philadelphia office successfully brought a number of splashy public corruption cases, including the racketeering conspiracy case against Fattah, convictions of more than 25 police officers for crimes ranging from theft to drug trafficking, and a case that led to ouster of nearly every sitting judge of the now-defunct Philadelphia Traffic Court.

But it also endured tough losses in a case against reputed former mob boss Joseph Ligambi, which twice ended in a hung jury before prosecutors withdrew the charges in 2014, and a bitterly fought courtroom battle against six Philadelphia narcotics officers charged with shaking down drug dealers, which ended last year in acquittals.

Memeger's attorneys led the Justice Department effort in 2013 that resulted in a $2.2 billion settlement with Johnson & Johnson over illegal promotion of prescription drugs - one of the largest pharmaceutical settlements under the False Claims Act.

"His office has prosecuted terrorists, corrupt public officials, dangerous drug dealers and other violent offenders, child predators, human traffickers, and perpetrators of serious fraud," Attorney General Loretta Lynch said in a statement. "There is no doubt that our country is safer and stronger thanks to Zane's exceptional contributions and dedicated efforts."

Colleagues said Tuesday that Memeger's work outside of the courtroom might be his most significant legacy. More than his predecessors, he steered time and resources toward communities affected by violent crime, and sought to raise awareness about the difficulties facing prisoners after their release.

When Linda Cliatt-Wayman, principal of Strawberry Mansion High School in 2012, reached out to him over concerns about gang violence, Memeger committed fully, she said.

Over the past four years, the U.S. Attorney's Office has led a number of antiviolence initiatives at the campus and helped secure for the school a football practice field and a community garden.

"He felt that it was important that his people actually do the work in this community," she said. "Like he said, 'We arrest so many people in this community, we have to do something to give back to the community.' He believed and his people believed it."

Memeger's resignation follows those of Peter J. Smith and David J. Hickton, the U.S. attorneys for Pennsylvania's two other federal judicial districts, who announced their intentions to step aside earlier this year.

The post traditionally goes to a member of the president's political party, with the White House turning to a state's U.S. senators for guidance in filling it.

Sens. Pat Toomey (R., Pa.) and Bob Casey (D., Pa.) have not said whether they have begun compiling a short list of replacements.

Several potential candidates have been suggested in legal circles, including Delaware County District Attorney John J. Whelan; James Schultz, general counsel under Gov. Tom Corbett; Chester County District Attorney Thomas Hogan; and former federal prosecutors William McSwain, now with the Center City law firm Drinker, Biddle & Reath, and Joseph Poluka, now with Blank Rome.

Ronald D. Castille, a former Philadelphia district attorney and retired chief justice of the Pennsylvania Supreme Court, has also expressed his interest in the job.