According to Merrillville police, Cash Irby Jr. found the gun in his parents' bedroom closet and brought it to his room when it fired once, hitting the boy in his head.
Cash was unresponsive when police arrived, and declared dead at nearby Broadway Methodist South Hospital.
According to a family member, the gun was stored responsibly.
"They always kept it it up in the closet behind shoes and clothes and boxes," Kelly White-Gibson, whose exact relationship to Irby is unclear, told WGN. "We're not sure how he ever saw it."
Police say the boy likely had to climb on something to be able to even see the firearm, but child protective are investigating.