A 14-year-old Alabama boy has been charged with murder in the death of his half-sister, after the 9-year-old was found hanging from a tree.

Katelynn Arnold's aunt found the girl hanging from a tree near their home Thursday night, the Birmingham News reported. Katelynn and her half-brother both lived with their aunt and uncle, their foster parents, in the 1,900-person town of Ragland.

St. Clair County Sheriff Terry Surles told the newspaper the accused boy, who has not been named, admitted to killing Katelynn by hanging her with a rope. She had apparently been riding her bicycle when her half brother called her over near a tree.

The boy reportedly gave investigators a motive for the killing but Surles did not release it.

The little girl's aunt did not realize she was missing until 7 p.m., at which point she drove around looking for her for 45 minutes before finding her. Surles said a cotton rope was tied around her neck but not in a hangman's noose.

The Birmingham News reported the boy went to bed after Katelynn was taken to the hospital, where she was pronounced dead. He was arrested later that night around 2 a.m.

"She never got a chance to grow up. Her life was taken away," neighbor Ricky Campbell told the Birmingham News.

Campbell, who told WBRC-TV his granddaughter was Katelynn's best friend, said he never saw any real signs of trouble from the boy.

"He'd run off and do crazy things, but I never believed he'd do something like that. It's a bad situation," he said.