"I assume he's seen this on video games or TV. I don't know if he knew exactly what this would do. I can't answer that. I do know it's a tragedy."

The children's mother was in another room, feeding other children lunch at the time of the incident.

Police are still investigating the circumstances of the shooting, including how the weapon - a .25 calibre handgun - was accessed.

"This is all new ground for us, we've never dealt with a kid shooting a kid at age nine," Sheriff Cantrell told local press.