The top federal prosecutor in Atlanta abruptly resigned this week and President Trump bypassed his top deputy in selecting a temporary replacement — an unusual set of moves, even in the administration’s waning days.

On Monday, Byung J. “BJay” Pak, whom Trump had appointed as the U.S. attorney for the Northern District of Georgia in 2017, unexpectedly told colleagues he was stepping down.

Then, on Tuesday, officials announced that Trump had installed Bobby L. Christine, the U.S. attorney in the Southern District of Georgia, to replace Pak on an acting basis, even as he maintained his current role.

Departures of U.S. attorneys late in the administration are commonplace, and many appointed by Trump already have left or announced plans to do so. But Pak’s departure took colleagues aback because of its swiftness. That day, Pak was supposed to participate in a meeting with former federal prosecutors, but suddenly called it off, people familiar with the matter said.

His departure also came just a day after The Washington Post reported on an extraordinary call in which Trump urged Republican Brad Raffensperger, the Georgia secretary of state, to “find” enough votes to overturn his election defeat in that state. Legal scholars said the request from Trump was an obvious abuse of power that might warrant criminal investigation.

In the same conversation, Trump cited a “never-Trumper U.S. attorney” in Georgia — a possible reference to Pak — and hinted vaguely and baselessly that Raffensberger’s refusal to act on his unfounded fraud claims constituted a “criminal offense.”

“The circumstances here raise troubling questions,” said John Horn, a former federal prosecutor and U.S. attorney in Atlanta. “The normal transition of leadership goes to the first assistant, especially in this late phase of an administration with only days left to the term. This appointment bypasses a 20-year DOJ prosecutor who is incredibly regarded in every area of federal practice, and who has served superlatively as second-in-command in managing the office for more than half a decade. I just can’t think of any valid reason that justifies bringing in an outsider to lead the office under these circumstances.”

A spokesman for the U.S. attorney’s office in the Northern District of Georgia declined to comment on the reasons for Pak’s departure. Pak himself did not return messages. A spokesman for the U.S. attorney’s office in the Southern District of Georgia pointed to a news release announcing Christine’s appointment but did not respond to other inquiries.

The news about Pak was first reported by Talking Points Memo and later confirmed by a spokesman for his office. In the news release announcing his departure, Pak gave no reason for leaving so suddenly and expressed thanks to Trump and others.

“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 said in the news release. “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. I am grateful to President Trump and the United States Senate for the opportunity to serve, and to former Attorneys General [Jeff] Sessions and [William P.] Barr for their leadership of the Department.”

Pak — who was born in Seoul and immigrated to the United States when he was 9 — had previously served as an assistant U.S. attorney in the Northern District of Georgia. From 2011 to 2017, he served as a lawmaker in the Georgia House of Representatives. He is a Republican.

Pak’s replacement, Christine, had been appointed by Trump and confirmed by the Senate as the U.S. attorney in the Southern District of Georgia in 2017, and officials said he would continue in that role while he took over leadership of the Northern District.

An online biography indicates that Christine was given the role in the Northern District “by written order of the President.” In appointing him, Trump bypassed Pak’s deputy, longtime federal prosecutor Kurt Erskine, who would have otherwise assumed the acting job by default.

Before becoming U.S. attorney, Christine had worked as a prosecutor in the district attorney’s office in Augusta and as a judge in the Magistrate Court for Columbia County. He also serves in the National Guard as a one-star general and assistant to the guard’s chief counsel.

Julie Tate contributed to this report.