A five-year-old has accidentally shot dead his two-year-old sister as he played with his own rifle.
The tragedy happened on Tuesday afternoon at a home in southern Kentucky.
Cumberland County coroner Gary White told the Lexington Herald-Leader it was "just one of those crazy accidents."
The boy had picked up the .22-calibre Crickett gun, which he was given as a birthday present last year, when it went off.
Police said the family did not realise it was loaded. The children's mother was at home at the time but had just stepped away.
"She was actually cleaning her house, and she had went out on the porch," the coroner told WKYT-TV.
"She said no more than three minutes had went by and she actually heard the rifle go off. She ran back in and found the little girl."
The child was pronounced dead at Cumberland County Hospital from a single gunshot wound to the chest. Doctors worked on reviving her for about an hour without success.
The coroner said the shooting would likely be ruled as accidental, but Kentucky State Police spokesman Billy Gregory said it was unclear if any charges would be filed.
"Down in Kentucky where we're from, you know, guns are passed down from generation to generation. You start at a young age with guns for hunting and everything," Mr White said. "Accidents happen with guns."
The children are not being identified because of their ages.
Keystone Sporting Arms produces Crickett and Chipmunk rifles for children. They come in various colours, including blue and pink.
The company's slogan is "my first rifle", and its website features a section showing children on bird and deer hunts.