The teen was in the 8200-block of South St. Louis Avenue in Ashburn just after 3:10 a.m. when he was shot in the head, police said. He was taken to Christ Hospital in critical condition, police said.
A 43-year-old man suffered a graze wound to the nose, and was taken to Christ Hospital in good condition, police said.
CPD did not immediately provide information about what led up to the shooting.
No one was in custody later Monday, and Area One detectives are investigating.
Dozens have been shot in Chicago over Labor Day weekend.
INTERACTIVE SAFETY TRACKER | Track crime and safety in your neighborhood