Ferguson Mayor James Knowles announces the resignation of police Chief Thomas Jackson during a news conference on Wednesday in Ferguson, Mo. Jeff Roberson/AP hide caption

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Loretta Lynch has handled or supervised a wide range of cases including New York police brutality against a Haitian immigrant, a $45 million cybertheft involving ATMs and the ongoing fraud prosecution of Republican Rep. Michael Grimm of New York. Seth Wenig/AP hide caption

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U.S. Attorney General Eric Holder, shown speaking at the Congressional Black Caucus legislative conference on Friday, will be stepping down from his position as soon as a replacement is appointed. T.J. Kirkpatrick/Getty Images hide caption

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Attorney General Eric Holder speaks during a Sept. 4 news conference at the Justice Department in Washington. Pablo Martinez Monsivais/AP hide caption

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In the past year, the U.S. prison population fell by roughly 4,800, the first time in decades the number has gone down, according to the Justice Department. Attorney General Eric Holder discussed the findings in New York on Tuesday. Julio Cortez/AP hide caption

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A memorial sits at the site of Michael Brown's death in Ferguson, Mo. Any investigation into his shooting by a police officer is likely to take months. Larry W. Smith/EPA/Landov hide caption

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Attorney General Eric Holder testifies before the House Judiciary Committee on the oversight of the U.S. Department of Justice on Capitol Hill in Washington, Tuesday. Manuel Balce Ceneta/AP hide caption

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