A boy of 13 filmed his female friends torturing a girl for 45 minutes.
He goaded the girls into kicking, punching and stripping the 14-year-old.
And he ordered the attackers – aged 13 and 14 – to kick the victim’s head like a football on the count of three.
One of the thugs battered the victim with her stilettos, warning the girl she was “going six feet under”.
And the boy made her lick her blood off his shoes because his mum would “go daft” at him for getting them dirty.
Details of the ordeal in an Edinburgh underground car park were revealed at the High Court in the city yesterday.
The attackers – who can’t be named for legal reasons – admitted assaulting the girl to the danger of her life.
Outside court, the victim’s sister, 21, branded them “animals”. She said: “No matter what age they are, it is absolutely horrifying.
“I feel complete disgust that children of this age can do something like that.”
The court heard the assault happened at the Omni Centre after all four had been to a youth cafe together.
An argument broke out in the car park and quickly turned violent.
The boy filmed the assault on his phone, likening it to the zombie-bashing horror movie Resident Evil.
One of the group ripped a metal sign from the wall and the boy shouted, “break her jaw, smack her head off the wall” and “look at the wall, it’s covered in blood.”
Alex Prentice, QC, prosecuting, said: “The complainer pleaded to be left alone. The complainer was covered in blood and the 13-year-old shouted at her, stating that if she went to the police she would murder her.”
The victim’s ordeal only ended when the group were disturbed by another girl who ran off to call for an ambulance.
A security guard found the victim naked and covered in blood and pleading: “I need help.”
She was rushed to Edinburgh Royal Infirmary where she was treated over six days for injuries to her ears, eyes, legs, feet, knees, hip, shoulder, arms and hands.
Doctors believed the ferocity of the attack could have killed her.
Mr Prentice added: “The victim thought she may have died had someone not entered the car park.”
Lord Malcolm ordered all three to be detained in a secure school pending reports before sentence next month.