A three year-old boy has accidentally shot and killed his nine-year-old sister in Birmingham, Alabama.

Kimi Reylander died after being shot in the head by her brother in their great grandparents’ house in the suburb of Irondale, local Police Chief Ken Atkinson told AL.com.

Mr Atinkson said the boy found a loaded pistol on a bedroom nightstand and accidentally pulled the trigger, shooting his sister in the head.

The loaded gun had reportedly been left there by the victim’s great grandfather, Joel Watson, who did not know the children were visiting.

Kimi Reylander was flown with life-threatening injuries to Children's Hospital of Alabama, where she later died.

The police chief said that the incident appeared to be a "tragic accident" but that an investigation is under way to learn exactly what happened.

The nine year-old's great grandfather told WIAT.com: “It’s the worst thing I’ve ever done. This felt worse than losing my old mum and dad.

“This was my baby. She was my pride and joy.”