A man died when he and his son were pelted with sticks and stones as they played cricket, a court has heard.
Ernest Norton lived a "fit and active" lifestyle
The Old Bailey heard the pair were attacked by a jeering mob of children aged between 10 and 13.
Ernest Norton, 67, was at Erith Leisure Centre in south-east London in February 2006 when he was hit on the head by a missile and suffered a heart attack.
Prosecutors said the five accused, who deny manslaughter and violent disorder, were jointly responsible for the death.
The court heard Mr Norton was playing cricket on an outdoor pitch with his 17-year-old son James when up to 15 youths gathered at the fence and began shouting abuse.
David Fisher QC, prosecuting, said: "As the abuse worsened, the group began throwing stones and pieces of wood at father and son.
"Ernest Norton was struck at least twice on the head by these missiles.
"One of the stones hit him on the left side of his face causing a fracture to his cheekbone."
He suffered a heart attack and, despite receiving medical attention at the scene, died later that afternoon.
Mr Fisher said the mob, including the five accused, ran off after the "unnecessary, pointless and random attack".
The court was told a young girl had witnessed the attack and named a boy who had thrown a large stone, the size of half a brick, which hit Mr Norton on the head.
Jurors heard Mr Norton, who lived with his wife and son in Erith, had undergone a triple bypass operation in 1977 but had a "fit and active lifestyle".
The prosecution said he was in good health on the day he died but "the stress and trauma of abuse and a physical attack would make him vulnerable to a heart attack".
Those accused include two brothers aged 12 and 13, one boy aged 13 and two 14-year-olds. Mr Fisher said "their youth is no defence".
"They were quite old enough to know that to abuse Ernest Norton and his son was wrong and that to throw stones and pieces of wood at them was wrong.
"It was their joint course of conduct, quite probably with others, that caused his death."
The case continues.