Chicago Inspector General Joe Ferguson will be stepping down from the post he’s held for 12 years this fall if the City Council doesn’t renew his soon-to-be expired term as City Hall’s main watchdog.

But that message got muffled in a letter Ferguson sent to Mayor Lori Lightfoot and the chairmen of the City Council’s budget and ethics committees Thursday evening, as first reported by The Daily Line.

The letter warns aldermen about the complex process to replace him, but it reads more like a resignation letter with Ferguson announcing he’d be stepping down by end of business on Oct. 15, the day his six-year term expires. Ferguson would not talk to WBEZ on the record about the letter.

Speaking after Friday’s special City Council meeting, Lightfoot said she learned about the letter during the meeting and thanked Ferguson for his “tremendous work” as the city’s inspector general, adding, “We will follow the ordinance for finding a successor to him.” But Lightfoot has indicated in the past that she wasn’t sure she’d reappoint Ferguson to the position.

Serving under three mayors, Ferguson has been at the helm of an investigative office that has grown significantly over the years. After the police killing of Laquan McDonald, the City Council dramatically expanded the office to serve as a check on the Chicago Police Department.

A new position of Deputy Inspector General for Public Safety was created, along with an entire team dedicated to tracking policing trends. Some of those positions are now protected under a federal consent decree that puts additional pressure on the City Council to find Ferguson’s replacement.

Before that, in 2015, the City Council reluctantly expanded the powers of the Inspector General’s Office to investigate aldermen and their staff.

And that is where Ferguson’s planned resignation gets complicated.

It’s no coincidence that three sitting members of the City Council are currently under indictment after the inspector general was given the authority to investigate aldermen and their staff. Federal prosecutors have acknowledged Ferguson’s office provided assistance in the investigations in all three cases.

Now, those indicted aldermen and the rest of their colleagues will be required to approve his replacement.

When aldermen were considering giving Ferguson the authority to investigate the City Council a few years ago, Ald. Ed Burke, 14th Ward, tried to block it with a watered down version of the ordinance, warning his colleagues they’d regret it. Burke is one of those three aldermen currently under indictment after he allegedly shook down the owner of a Burger King in his ward who came to Burke for a routine permit.

Another longtime critic of Ferguson, Ald. Carrie Austin, 34th Ward, and her chief of staff were indicted this week for allegedly taking bribes from a developer doing work in her ward. The press release from the U.S. Attorney’s Office released Thursday mentions cooperation from Ferguson’s office.

Austin once characterized Ferguson’s office as conducting a “witch hunt” against her and her family, many of whom were on the city payroll, as reported by WBEZ.

It’s likely that Burke and Austin, and Ald. Patrick Daley Thompson, 11th Ward, who also is under federal indictment, will still be on the City Council when it’s time to vote on Ferguson’s successor.

Claudia Morell is a metro reporter for WBEZ. Follow @claudiamorell.