Chicago Police Department's future leadership uncertain as chief resigns, rumors swirl around supt.

CHICAGO (WLS) -- There is uncertainty over the future of top leadership for the Chicago Police Department.

Chief of Detectives Brendan Deenihan is leaving his position, and the fate of the mayoral election could determine the future of Superintendent David Brown.

With crime as the top mayoral campaign issue, Brown has been written off by all the candidates, except one: the person who hired him. Mayor Lori Lightfoot vows Brown is going nowhere as reports of his resignation swirl.

"Supt. Brown is not leaving," Lightfoot said. "Supt. Brown is hard at work every single day making sure our communities are safe."

Sources tell ABC 7 that Brown wanted to leave in January, but agreed to stay on until April 1, after the election. The mayor denied the reports while attending a campaign endorsement event Thursday with a group of South and West Side ministers.

"I think it's a disservice not only to him, but to the hard working men and women of the Chicago Police Department, that despite the fact that he has denied it, I deny it and the rumors persist and you report it as fact," Lightfoot said.

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However, Lightfoot said it is fact that Deenihan is leaving the force February 24 to reportedly take a job with Google.

"He's done great work as a chief," Lightfoot said. "We wish him the best."

Deenihan's departure is viewed as a huge loss for the department. He joined CPD in 1997 and worked his way up through ranks, earning himself the reputation as a well-respected leader.

"He was just a strong mentor within the ranks, just a brilliant law enforcement mind," 19th Ward Ald. Matt O'Shea said.

O'Shea works closely with Deenihan, and says his resignation just adds to the chaos within the department.

"I'm confident as always in the past has happened, younger leaders will step up, people who were mentored by Chief Deenihan," O'Shea said.

O'Shea said there are several strong commanders across the city that can step into his role. In the meantime, even if Supt. Brown were to stay on, he is only a few months away from mandatory retirement at the age of 63.