Police said the shooting happened near Ruble Street and Roosevelt Road in the city's South Loop neighborhood just before 4 p.m.
Chopper 7 was over the scene behind Bob's Discount Furniture, where officers could be seen investigating.
Police said a 23-year-old man was standing near the alley when a suspect approached him, took out a gun, and fired shots before fleeing the scene in an unknown direction.
The victim, shot twice in the leg and once in the chest, was transported to Stroger Hospital in serious condition.
Area Three detectives are investigating. Police did not immediately provide further information about the shooting.
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