The shooting happened around 12:38 p.m. in the 9200 block of South LaSalle Street, in the Roseland area, Chicago police said.
A 15-year-old boy was in an altercation with an unknown offender when they shot him in the chest with a firearm, police said.
The victim was taken to Christ Hospital in critical condition, CPD said.
The Cook County Medical Examiner's Office later confirmed the boy died. He was identified as 15-year-old Robert D. Gunn Jr.
No further information about the offender was immediately available as Chicago police continue to investigate.
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