Five teenagers were convicted today of chasing a 15-year-old boy from his school gates and stabbing him to death in a gang-related attack. Zac Olumegbon was knifed in the heart and also had wounds to his chest, neck and buttocks. His hands and arms were scarred showing that he had tried to ward off the blows. He was cornered by the youths wearing hoodies in a back garden 100 yards from the Park Campus school in West Norwood. Another schoolboy was also stabbed but Zac was the prime target in the attack in July last year. At the Old Bailey four of the youths were found guilty of murder and a fifth convicted of manslaughter. They can be named for the first time today after Judge Giles Forrester QC lifted an anonymity order. The murderers are Helder Demorais, now 17, Kyle Kinghorn, who is 18 today, Ricardo Giddings, 17, and Jermael Moore, 17. Moore was a promising grime artist, known as J-kid or Younger Sneaky, who had posted videos on YouTube under a gang name. Some of the footage, which includes the sound of shots being fired, shows hooded and masked youths making gun symbols with their hands as he raps lyrics. Shaquille Haughton, 16, was the youth convicted of manslaughter. They will be sentenced next month. The court heard that Zac was a victim of a feud involving the Gas gang, which stands for Guns and Shanks (knives), based around Loughborough Road and the Angel Town estate in Brixton. Their rivals were the The five youths arrived at the school by car knowing their victim would be turning up for class. The teenager had spoken at a conference on youth violence the day before and vowed to help other teenagers, his mother said in a statement. He wanted to share his experiences with those who had endured "similar struggles to him", said Shakira Olumegbon. She said he had left for school "happy" on the day of his death after discussing the future with her. But Ms Olumegbon received a phone call from school to tell her he had been attacked. She said: "I remember praying he would be okay. The scene that confronted me was indescribable."