Twenty-two-year-old Eddie Ramos faces a first-degree murder charge in the shooting death of Miguel Villalba last year in Cicero.
Cicero's police chief says the 15-year0old victim had been working to turn his life around.
"He was a little big troubled and had been part of the juvenile improvement program, and he successfully completed that program, and we were hoping it would change his ways," said Cicero Police Chief Bernard Harrison.
Ramos was arrested Tuesday. He is being held without bond.