A 9-year-old Florida boy who allegedly stabbed his 5-year-old sister — telling her, “Die, die” — will be charged with attempted first-degree murder, according to new reports.

The Ocala boy, whose name was not released because of his age, was playing in his room with his sister Monday afternoon when their mom slipped outside to check the mail, WKMG-TV reported.

When the mother returned, she found her son stabbing his sister repeatedly with a kitchen knife, the outlet reported.

She grabbed the knife from her son, who fled into a maintenance shed, and then picked up her daughter and called 911, authorities said. The girl was reported alert and responsive after the attack.

The boy told authorities that the thought of killing his sister “had entered his head two days earlier” and wouldn’t go away, according to an arrest report obtained by FOX 35.

He told cops he grabbed a knife from the kitchen, entered the bedroom, grabbed his sister by the neck while she was bent over and began attacking her, the station reported.

“Die, die,” the boy told his sister during the unprovoked attack, according to the report.

The boy allegedly told investigators he stabbed his sister because “he wanted to be able to go outside.”

Investigators found probable cause to charge the boy, the arrest report said.

He is being held in secured detention ahead of a psychiatric evaluation ordered by a Marion County circuit judge Monday.

A public defender has been appointed to represent the boy, who is set to reappear in court Feb. 5.