The boy has been identified to the Cook County Medical Examiner's Office as Jamonte Shaw.
Community activists who responded to scene said they hope this serves as a reminder for parents and caregivers to secure your firearm around children.
Police said it happened Sunday afternoon inside a home on 104th and South Maryland streets.
The child was rushed to Comer Children's Hospital in critical condition, where he later died.
Detectives and evidence technicians on scene and the hospital are now trying to piece together how this happened
"We could talk about the lessons and things that we all have to learn from this, but the tragedy I think at this point, and the pain the family's feeling, and the pain that we all should feel for this child who was just beginning," Pastor Donovan Price. "We can't keep losing our babies because of some adult things, and so, whether it's gun locks or gun safety kits, or whatever the case may be, or just plain paying attention, we got to be proactive or pray active."
It's unclear exactly how the toddler was able to access the gun.
Police said a 31-year-old man is now in custody.
No word yet about possible charges, nor have police said what his relationship is to the toddler.
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