Three youths face life sentences after being found guilty today of murdering schoolboy Nicholas Pearton.
The 16-year-old was chased across a park in daylight and killed by a gang of schoolchildren last May.
Some of the youngsters were still wearing their school blazers and ties as they hounded Nicholas with knives and other weapons, the Old Bailey heard.
Within minutes, he was dead, stabbed in the back in the street and lying in a pool of blood in a shop where he took refuge.
His parents, who lived near Home Park, Sydenham, south east London, ran to the area but could not help him because his body was lying across the door.
Two 17-year-olds and a 16-year-old were found guilty of murder. Another 17-year-old was found guilty of manslaughter.
A 14-year-old and a further 16-year-old were cleared of charges.
The convicted youths, who cannot be identified for legal reasons, were remanded in custody for sentencing next month.
Edward Brown QC, prosecuting, told the court that the violence was the result of a clash between two gangs - the Shanks & Guns and the rival Black Mafia.
Nicholas died after the knife pierced his heart when the mainly 15 and 16-year-old members of the S&G gang chased him through the park.
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.
"More than one of those hounding down Nicholas Pearton was armed with a knife."
Mr Brown said Nicholas was the only white boy involved in the incident that afternoon.
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, a friend, a member of Black Mafia - also known as the Sydenham Boys - had been involved in a row at school with a 17-year-old.
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.
"What happened thereafter, as described by one witness who saw the defendants as they ran Nicholas Pearton to ground and killed him, was a group of young men acting 'like animals'.
"He was an easy and vulnerable target on his own. He was chased across the park, described as 'running for his life'.
"He was caught by two or three at least in Sydenham Road. It was there that he was stabbed by the front runner."
Mr Brown showed the jury dramatic CCTV footage of Nicholas's last moments as he ran to a chicken shop and slumped on the floor.
"Nicholas Pearton's mother was close by and had been alerted to her son being in the park and potentially in danger.
"She came on to the scene after her son had been injured. In those dreadful and deeply distressing moments she saw her son lying dead or dying inside the door of the shop.
"His father too was soon on the scene, also very distressed," Mr Brown told the jury.
He said that, after the stabbing, the group discarded their weapons as they made off, laughing and joking.
"One was seen to hold a knife high above his head, as if bragging at what had just happened," he added.