Updated 06/25/12 – 1:17 p.m.

CHICAGO (CBS) — Veteran federal prosecutor Gary S. Shaprio will take over as acting U.S. Attorney when Patrick Fitzgerald steps down at the end of the week.

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Fitzgerald is stepping down at the end of the month after almost 12 years in office. He took over on Sept. 1, 2001, making him the longest-serving U.S. Attorney for the Northern District of Illinois.

Shapiro has been the top deputy at the U.S. Attorney’s office in Chicago for 14 years, since before Fitzgerald became the district’s top prosecutor, and has been a federal prosecutor in Chicago for 40 years.

“Gary Shapiro is a prosecutor’s prosecutor. The Office could not be in better hands.” Fitzgerald said in a news release Monday. “As a trial lawyer and organized crime supervisor, he fearlessly pursued mobsters as well as corrupt politicians and union leaders in cases that were historic in significance. In his two decades as Criminal Chief and First Assistant, he has consistently exhibited great leadership and integrity, while providing wise counsel and guidance on a wide variety of cases. Gary has seen it all.”

U.S. Sen. Dick Durbin said Monday that he and U.S. Sen. Mark Kirk — who is still recovering from a stroke — will work together to find a full-time replacement for Fitzgerald, and will appoint a six-member panel to screen applicants.

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Durbin said he and Kirk want a completely bipartisan or nonpartisan candidate to take over for Fitzgerald.

“We are going to appoint a separate committee from those that have previously been appointed; three each to the committee, and each name a co-chair, so that those six people will consider and review all applications for this position,” Durbin said.

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Durbin and Kirk will interview all finalists for the job, and pass on a recommendation to President Barack Obama. The president’s nomination for the post would have to be confirmed by the U.S. Senate.

Shapiro will be free to apply for the full-time job.

Durbin said he discussed the selection procedure with Kirk during a phone call, and that Kirk’s ideas and speech were both clear as he continues rehabilitation from the stroke suffered in January.

Shapiro managed the U.S. Attorney’s offices in Chicago and Rockford under Fitzgerald, overseeing 170 assistant U.S. attorneys in all.

In his position as First Assistant U.S. Attorney, and as Criminal Chief for six years before that, Shapiro, 65, supervised investigations and prosecution for high-profile cases involving international terrorism, public corruption, corporate fraud, and organized crime, the U.S. Attorney’s office said.

Fitzgerald has said he plans to take some time off this summer to spend more time with his wife and children, before deciding what to do next in his career. His last day on the job will be June 30.

Durbin said Fitzgerald “has done an extraordinary job, and enjoys a strong reputation in a state which has been battered with political prosecutions. He’s been even-handed, he has gone after leaders in both political parties, and has really written an incredibly great record of integrity and skill.”

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Fitzgerald became a national celebrity for going after political corruption in Illinois. Most notably, he led the prosecutions of both Gov. George Ryan and Gov. Rod Blagojevich, who are both serving time in prison.