Michael Colon, 16, was shot on Sept. 3, while walking his dog.
Chicago police still don't have any suspects.
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"We've raised the reward because these murderers do not deserve to be walking the streets," Colon's sister Joanna said.
Police said a white SUV was seen in the area just before shots were fired. The car reportedly sped away right after the shooting.
Anyone with information is asked to call a tip line Colon's family provided at 224-651-6662.