The shooting took place at a home on Sunday afternoon, authorities said. The boy's family members told authorities they heard a gunshot while in another room and then found the boy with a gun, according to Chicago police spokesman Anthony Guglielmi.
No arrests have been made, Chicago Police spokeswoman Sally Bown told ABC News on Monday.
"We extend our deepest condolences as detectives continue to investigate," Guglielmi tweeted. "DCFS [the Department of Children and Family Services] has also been called in to assist."
Hunter said a child unintentionally shoots themselves or another child eight times every day, citing a multi-year average of data compiled by the Centers for Disease Control and Prevention.
"The most important thing that parents can do is if they choose to bring a gun into the home is to store it safely," Hunter told ABC News in May. "And what we know from research is the most safe way is unloaded, locked, and with the ammunition stored separately."