The youngster was due to go on trial this week accused of murder. He is due to be sentenced on 1 December.
A 13-year-old boy has made a confession before a court.
He pleaded guilty to causing the death of a grandmother fatally hit by a car in Sheffield.
The boy, who cannot be named for legal reasons, appeared at Sheffield Crown Court on Tuesday, October 3 via video link and admitted to causing the death by dangerous driving of 60-year-old Marcia Grant by running her over with her own car in Greenhill on 5 April, when he was 12.
The boy previously admitted a second charge of possession of a kitchen knife.
When he first appeared before court in April, prosecutor Gary Crothers told Sheffield Youth Court that police at the scene noted that the boy said "Is she dead?", "Looks like I got my first kill?", and "It was an accident, I swear."
His lawyer, Ben Campbell said the issue in relation to these comments was "what you can infer from them in all the circumstances".
Describing the incident, Mr Crothers told the youth court: "At around 7pm on the evening in question this defendant is seen on CCTV attempting to take Mrs Grant's car.
"Mrs Grant tries to stop him by going behind the car.
"On CCTV, the vehicle is driven slightly erratically at this time and it does come to a stop.
"Mrs Grant positions herself behind the vehicle. The vehicle reverses, causing her to fall on her back and her head impacts with the ground.
"She was trapped under the vehicle, her husband tried to break the window of the car to get the defendant out of the car."
The prosecutor said the vehicle then reversed "at some speed causing the catastrophic injuries to Mrs Grant".
Emergency services had been called outside her house but she was pronounced dead at the scene.
The youngster was due to go on trial this week accused of murder. He is due to be sentenced on 1 December.
Mrs Grant's family released a statement after her death, describing her as a "warm, loving and dedicated wife, mother, grandmother, sister and friend and a pillar of her community".