Chicago's top cop responds to his firing after he's found asleep in squad car

Chicago's ousted police chief broke his silence on Tuesday, a day after the city's mayor revealed that he'd been fired over "ethical lapses."

Mayor Lori Lightfoot fired Superintendent Eddie Johnson on Monday, less than a month before he was scheduled to retire, accusing the top cop of misleading city officials and the public after officers found him asleep in his vehicle in October.

Johnson acknowledged on Tuesday that he made a "poor decision and had a lapse of judgment" on that October night, an incident he previously blamed on a problem with his medication. Johnson said he had pulled over because he was feeling light-headed, later falling asleep.

He called it "a mistake," but maintained that he did not "intentionally mislead or deceive the mayor or the people of Chicago."

"I know in my heart that I have always tried to act in a way that is in the best interests of the great city," Johnson said in a statement, noting that he had no interest in fighting for his reputation. "Reputations are not built in a day and not damaged in a day either."

"I will simply rely on the reputation for integrity that I think I have earned during my long career, with the faith that we should all be judged by the entirety of our lives and not on what happened on our worst days," he added.

An official briefed on the probe into Johnson's conduct told ABC News that during the traffic stop in question, the superintendent showed his police ID when asked to present identification. The officers apparently didn't recognize Johnson immediately. Once the superintendent showed ID, he and the officers exchanged some words, and Johnson said he was OK to drive away. The cops let him, raising questions about why Johnson wasn't given a field sobriety test.

Lightfoot said an inspector general's report, which hasn't been released publicly, showed Johnson exhibited "flawed decision-making."

"It has become clear that Mr. Johnson engaged in a series of ethical lapses that are intolerable," Lightfoot said in statement Monday. "Mr. Johnson was intentionally dishonest with me and communicated a narrative replete with false statements regarding material aspects of the incident that happened in the early morning hours of October 17."

"Had I known all the facts at the time," she added, "I would have relieved him of his duties as superintendent then and there."

ABC News' Stephanie Wash and Josh Margolin contributed to this report.