Updated 2 p.m. ET Tuesday

The top U.S. prosecutor in Atlanta resigned from his post Monday, giving no clear reason for his departure.

The resignation of Byung J. "BJay" Pak, who was appointed U.S. attorney for the Northern District of Georgia by President Trump, came justone day after a phone call between the president and Georgia Secretary of State Brad Raffensperger was made public, during which Trump urged Raffensperger to "find" enough votes to overturn his loss in the state.

In the call, Trump, talking about investigations into claims of voter fraud, referred to a "never-Trumper U.S. attorney" in Georgia, according to The Associated Press. It's unclear, however, whether Trump was referring to Pak.

The online news site Talking Points Memo reported that Pak wrote in an internal email dated Monday that his departure was due to "unforeseen circumstances."

Pak was replaced by Bobby Christine, U.S. attorney for the Southern District of Georgia, also a Trump appointee. The Southern District's website said Christine was appointed acting U.S. attorney for the Northern District of Georgia on Monday "by written order of the President."

"It has been the greatest honor of my professional career to have been able to serve my fellow citizens as the U.S. Attorney for the Northern District of Georgia," Pak wrote in his announcement. "I have done my best to be thoughtful and consistent, and to provide justice for my fellow citizens in a fair, effective and efficient manner."

Pak served in the role since October 2017. Talking Points Memo said Pak originally intended to stay in office until President-elect Joe Biden's inauguration on Jan. 20. New presidential administrations usually replace U.S. attorneys from prior administrations; however, it's not usual for them to leave before the end of their term.

Pak, who was born in South Korea, immigrated to the U.S. when he was 9. As U.S. attorney, the Justice Department said, his office increased the number of criminal cases prosecuted by more than 30% compared with 2017.

Prior to serving as the Atlanta area's top federal prosecutor, Pak was a member of the Georgia House of Representatives from 2011 to 2017. As an attorney, Pak started out in private practice and later worked as an assistant U.S. attorney in the Northern District of Georgia.

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