Harris County District Attorney Kim Ogg's top lieutenant is out the door after the latest staffing shake-up at an office already plagued by high turnover and ongoing retention problems.

Tom Berg, a former defense attorney who came on board at the start of Ogg's administration, confirmed his departure early Tuesday - and though initially he described it to the Chronicle as a firing, officials later said that he resigned when offered a different job title.

"I realize that as the office has evolved its needs have necessarily changed," Berg wrote in a letter to Ogg dated Tuesday. "I could not anticipate or adjust to each aspect of the transformation and acknowledge your need to have a First Assistant who is philosophically more aligned with your course for the future."

It's not clear if a specific incident prompted the move. Two other employees - Human Resources Director Dean Barshis and Community Outreach Coordinator Shekira Dennis - are shifting roles in similarly unclear circumstances.

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READ MORE: High turnover continues at Harris County DA’s office

When Ogg took over the office in January 2017 after ousting Republican incumbent Devon Anderson, she made waves by letting go dozens of veteran prosecutors and replacing them with a number of seasoned defense attorney - including Berg.

"Change is coming," Ogg said at the time. "Like any good team that has suffered some under-performing seasons, we're changing management. My administration is heading in a new direction."

But even after Ogg took the helm, the changes continued. As of April, more than 140 prosecutors had left under her tenure, generating a sharp uptick in turnover.

Ogg has attributed the turnover to fallout from Hurricane Harvey, which has left courtrooms scattered across a number of buildings and prosecutors working in makeshift offices.

Some local attorneys chalked up the departures to leadership issues.

"There's a lot of different things going around — they're overworked because of the hurricane or they're not going to trial — but really it's that there's no leadership," said Josh Phanco, a longtime felony prosecutor who left the office earlier this year. "There's no one you look at and say, 'Oh, I want to be that guy.' They all got fired."

In the years before he joined the district attorney's office, Berg served in the military in Iraq, Afghanistan, and Bosnia-Herzegovina. He is a Washington, D.C. native later raised in Mexico City.

After graduating from Rice University and the University of Houston, he worked as a military lawyer challenging the government's alleged use of torture at Guantanamo Bay.

"He put his own career in jeopardy because he believes in the higher principles of law," Ogg said in a 2017 news release announcing his hire. "Anybody with that kind of character, along with 40 years of experience, has the kind of qualifications we need in this office."

He also spent more than a quarter century at the Federal Public Defender's Office in Houston, serving as the First Assistant there for 19 years.

READ MORE: Shake-up at the courthouse: Incoming DA Ogg hands pink slips to 37 top prosecutors

Berg's last day in the office is Wednesday. His sudden departure immediately sparked speculation and surprise in the legal community.

"You have a lot of different people leaving," said Murray Newman, a defense attorney and former prosecutor. "If you look at Tom Berg as a good, ethical, stable force and he's at the top and he's leaving it doesn't give you a whole lot of hope for the people who are practicing below him."

Officials have not yet said who's replacing him or what alternative position he was offered, and Berg did not offer additional comment.

Meanwhile, Yvonne Taylor is stepping in as acting director of Human Resources. Officials would say only that Barshis is still on the payroll.

Dennis will continue working for the district attorney's office but as a contractor, employed by her own public-engagement firm.

keri.blakinger@chron.com, @keribla