CPD said the incident took place on the platform stairs in the 0-100-block of East Roosevelt Road, just before noon on Monday.
The Roosevelt station is located in that block.
The suspect is described as wearing a black sweater, black pants and white sneakers.
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CPD did not immediately provide any additional information on what led up to the attack.
Anyone with information is asked to call Public Transportation Detectives at (312) 745-4447 or submit an anonymous tip at CPDTIP.com.
This is a developing story; check back with ABC7 Chicago for updates.
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