CPD did not immediately provide any additional information about the person.
Earlier Thursday, Chicago police released images of the man accused of shooting and killing two people at Navy Pier.
Police said a disgruntled employee shot two of his former co-workers at Navy Pier Tuesday afternoon.
He is described to be 6'2'' tall, and weighs about 230 pounds with black hair and brown eyes.
Chicago police said he fled the scene using public transportation.
Anyone with information is asked to call (312) 744-8261 or call 911.
READ ALSO | Disgruntled employee shoots, kills 2 at Navy Pier: Chicago police
The victims were identified as Lamont Johnson, 51, and Peter Jennings, 47, according to the medical examiner.
Johnson's aunt said he had worked at Navy pier for more than 20 years. The family is devastated by his death, saying he was a caring man who always helped those around him.
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