A 12-year-old girl in Tennessee has been charged with murder for allegedly smothering her 8-year-old cousin, who was asleep in their shared bedroom.

The incident, which occurred on July 15 in Humboldt, was captured on security camera.

The video shows the older girl using bedding to suffocate her cousin and then cleaning up the scene and repositioning the body afterward.

The two had been arguing over an iPhone. The girl has been charged with first-degree murder and tampering with evidence, ABC News has reported.

Gibson District Attorney Frederick Agee described the act as one of the most disturbing his office has handled and plans to petition for the girl to be tried as an adult, which could result in a lengthier sentence.

Written by B.C. Begley