It's still unclear how the baby fell from a high floor. The boy's death is especially painful for one neighbor who tried desperately to save his life.
Police said it happened at a residential building in the Edgewater neighborhood's 5800-block of North Sheridan Road around 11:30 a.m.
The child fell from the building's fourth floor and suffered a head injury, police said.
He was taken to St. Francis Hospital in critical condition. He later died at Lurie Children's Hospital.
The Cook County Medical Examiner's Office identified the boy as 1-year-old Mukhsin Mirzoshrafov.
What led up to the fall was not immediately clear.
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No other injuries were reported.
Area Three detectives are investigating.
Another building resident said he performed CPR on the child until paramedics arrived. He said his thoughts are with the family.
Marion Lenz said he was outside, in front of the building, when the child's father came rushing up to him, pleading for help, with the baby in his arms.
"I, you know, went in, got my phone, called 911. And as 911 was telling me how to do CPR until the paramedics arrived, and then the paramedics came and took over and all that stuff," he said. "I'm still in shock from it. Like, it was, like you're sitting there. And you're going through everything, and like I just kind of broke down afterward. It was crazy."
Residents say the windows of the building slide open sideways, and there are window screens, but again it's unclear how the child fell to the ground