CHICAGO -- Sources tell WGN that Chicago Police Supt. Eddie Johnson needs a kidney transplant.
He does not have diabetes, sources also say.
Earlier Friday, Johnson fell ill at a news conference where he and Mayor Rahm Emanuel were unveiling a new piece of technology.
He stumbled, and Emanuel and other officers helped him to a chair.
After the incident, a police spokesman said he felt light-headed and did not lose consciousness. He was able to walk out of the news conference and to his car with the mayor's assistance.
Johnson is expected to address the media Friday evening about his health.
This is a developing story. Check back for details.