New York, May 9: In what has seriously got to be one of the most disturbing stories ever, jurors in the murder trial of a 13-year-old boy accused of killing his mother heard the 911 call in which the teen confesses to shooting his mother 21 times with a rifle -- but not before trying to rape her. 

The Iowa teenager, Noah Crooks, calls 911 after the murder and rambles on for 10 minutes.

Crooks, now 14 , has been charged with first-degree murder and assault with intent to commit sexual abuse on March 24, 2012.

The victim was his 37-year-old mother, Gretchen Crooks, who had taken away his “Call of Duty” video game because he got bad grades in school, it was said.

The court heard Crooks admit that it was because of the game being taken away that he snapped.

In the 911 recording made on the night of the murder at the family's home in Osage, Iowa, Crooks can be heard telling the operator: “I'm not joking at all. She's dead. I'm scared. I killed my mom with my .22. I don't know why I did it.”

Police responding to the call found the woman shot multiple times, according to Mitchell County Sheriff's Office.

During the conversation, which lasted about 10 minutes, the boy repeated his confession several times The Global Gazette reported.

Noah rambled on about his mother making him homemade doughnuts earlier that night and expressed disbelief that he killed her after she did that for him.

He then revealed that his mother had taken away his Call of Duty video game because he got bad grades in school, and that is when he snapped.

Gretchen's bullet-riddled body was found stretched out on a coach.

Her pyjama top was undone and she was naked from the waist down, Halbach said in court.