A 16-year-old boy was hounded and killed in a park by a gang of schoolchildren, the Old Bailey heard.
Some of the youngsters were still wearing their school blazers and ties as they chased Nicholas Pearton with knives and other weapons and within minutes, he was dead, stabbed in the back and lying in a shop doorway, said Edward Brown QC, prosecuting.
He said the violence was the result of a clash between two gangs - the Shanks & Guns (S&G) and the rival Black Mafia.
Nicholas died after the knife pierced his heart after the gang of mainly 15 and 16-year-old members of the S&G chased him through Home Park, Sydenham, south-east London, in May last year, the court heard.
Mr Brown said: "Nicholas Pearton was chased across a public park by a group of young but armed teenagers. He was unable to escape. When he was caught he was stabbed and killed. Some of the defendants were in their school uniform at the time of the attack - in their blazers and ties. Indeed, the origin of the fatal violence in the park that afternoon may have been an incident earlier in the day at a school."
Six youths aged 14, 15, two aged 16 and two now aged 17, deny murder. They are all from the south-east London area but cannot be identified for legal reasons.
Mr Brown said it was alleged that one of the 17-year-olds stabbed Nicholas, but all the boys had been acting together. He added: "More than one of those hounding down Nicholas Pearton was armed with a knife. It may be that the defendant who was able to reach Nicholas first, the quickest runner, was the one who stabbed him."
Mr Brown said Nicholas was the only white boy involved in the incident that afternoon. He said he went to the park after receiving a call and telling friends that he had to go to help because S&G were there.
Three hours earlier, his friend, a member of Black Mafia - also known as the Sydenham Boys - had been involved in a row at school with the 17-year-old alleged knifeman, the court heard. This had led to a confrontation in the park between the two gangs. But by the time Nicholas arrived, his friends and the Black Mafia boys had gone.
Mr Brown said: "Moments after he arrived, his associates and friends, and therefore to a degree his protection, had evaporated. He was left on his own and isolated in the park. In the eyes of the defendants however, he remained a member of the rival Black Mafia gang." The hearing continues.