CHICAGO (CBS) — The head of Chicago’s FBI, who just arrived in January, already appears to be on his way out.

Sources tell the Chicago Sun-Times that FBI Special-Agent-in-Charge Cory Nelson, 51, is retiring from his post as head honcho.

With U.S. Attorney appointee Zach Fardon still to be confirmed by the Senate, Nelson’s surprise announcement would leave Chicago’s two top federal positions unfilled by permanent employees.

Nelson, who has held a remarkably low public profile since arriving in Chicago — even by FBI standards — notified the bureau on Wednesday of his intentions to move into the private sector in a position out of state, sources said. He had not granted media interviews in a time that Chicago Police Supt. Garry McCarthy was often in the spotlight.

Nelson came on board after long-time Chicago chief Rob Grant retired last year, following an eight-year stint.

Reached early Thursday, FBI spokeswoman Joan Hyde declined comment.

Insiders speculate that a combination of factors would likely lead to more such resignations throughout the country. For one, the cutbacks tied to the sequester had a stranglehold on bonuses that were once available to the FBI tops in field offices Also, President Barack Obama’s nomination of James Comey as the new FBI director is likely to mean a natural turnover of personnel who were close to previous FBI Director Robert Mueller.

It was immediately unclear how two changes at the top in Chicago in less than a year would affect the office that historically has had one of the most active public corruption units in the country.

On the prosecution side, the U.S. Attorney’s Office is also headed for change as it awaits confirmation of Zach Fardon at the helm in Chicago. Longtime hard-charging prosecutor Patrick Fitzgerald retired last year.

(Source: Sun-Times Media Wire © Chicago Sun-Times 2013. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)