CLEVELAND, Ohio -- A 3-year-old boy picked up a firearm inside an East Side home Sunday afternoon and the gun went off, hitting a 1-year-old boy in the head, Cleveland Police Chief Calvin Williams said.

The boy was taken to a nearby hospital and was later pronounced dead, according to police.

Investigators are trying to determine where the gun came from, Williams told reporters gathered outside the East 63rd Street home Sunday afternoon.

The gun was left inside the house unattended, and the person responsible for bringing the weapon into the home and leaving it where a small child could get to it will likely face charges, he said.

The full details behind the shooting aren't clear, Williams said, but at least one adult was home when it happened.

The boy's mother could be heard screaming on the back porch after she was told her son had died.

A crime scene investigation crew spent roughly an hour and a half at the two-story house Sunday, gathering evidence and interviewing witnesses.

A section of the street in front of the house was blocked off by yellow caution tape for several hours.

Neighbors said a mother lived in the house with at least three small children.

"They were really nice," next-door neighbor Larry Simpson said. "It's a shame this had to happen."