Members of a "Happy Slapping" gang today admitted killing a retired care worker in front of his young granddaughter.
The two, aged 15 and 16, pleaded guilty at the Old Bailey to the manslaughter of Ekram Haque, 67.
They also pleaded guilty to assaults on four other people before Mr Haque's death.
Another 15-year-old youth pleaded guilty to the other assaults which caused actual bodily harm. He denied manslaughter.
They cannot be named because of their ages.
They had all been charged with murdering Mr Haque last August in Church Lane, Tooting, south west London, as he walked home from a mosque.
He died from a head injury a week later. The attack was witnessed by his three-year-old granddaughter.
Brian Altman QC, prosecuting, told Judge Martin Stephens that the pleas were acceptable.
They were part of a "happy slapping" gang which called themselves Lane Gang Productions.
Detectives recovered at least six videos of "happy slapping" incidents taken from mobile phones.
No mobile evidence was recovered relating to the attacks in the charges and detectives are unable to say they were "happy slapping" incidents - only an escalation of their behaviour.
The defendants who admitted the killing were aged 14 and 15 at the time of the attack. The third youth was 14.
Judge Stephens remanded all three in custody to July 23 for sentencing.
The gang targeted vulnerable people in the area where a number of Asian people live.
The three teenagers pleaded guilty to causing grevious bodily harm to Atta-ul Hassan Mir and Imdad Bukari.
They were attacked in separate incidents just before Mr Haque as they left the mosque in Church Lane on August 31 during the Muslim festival of Ramadan.
The two youths who admitted the manslaughter also pleaded guilty to causing actual bodily harm to Jasumati and Jushbhai Patel on August 26.
They burst into the Tooting home of the couple, thought to be in their 70s, after being asked not to sit on their wall, and punched and stamped on them.
Mr Altman told the court that the pleas had been accepted in the light of all the circumstances.
There was CCTV footage of two of the youths striking Mr Haque from the front and back, and the third running off with them.
Mr Altman added: "There was evidence available to us to from mobile telephones of so-called Happy Slap-type activity in the week leading up to these events."
He said Mr Haque's death had resulted from an elderly and vulnerable man, minding his own business, being attacked, falling to the ground and suffering a head injury.