Five boys aged 12 to 14 have been locked up for two years each for killing a pensioner as he played cricket with his teenage son.
Ernest Norton, 67, came under a hail of sticks and stones as he and son James practised bowling together in February last year at Erith leisure centre in Kent.
Two stones, one the size of half a brick, struck the father of two on the temple and fractured his cheekbone, and he collapsed to the ground with a heart attack.
Five boys, one of whom was just 10 at the time, were convicted at the Old Bailey of manslaughter and violent disorder in August.
The youngest, now 12, and his brother, 13, as well as three other boys all aged 14 were given sentences in youth detention by Judge Warwick McKinnon.
The judge described their conduct as "utterly disgraceful and criminally irresponsible".
Some of the boys wept as they hugged their parents, many of whom were also crying, before being taken down.
The judge described it as a "sorry and tragic case".
He said: "A child would realise your actions were dangerous, running the risk that injury would result. I am satisfied that each one of you were aware of that danger.
"No sentence can restore the human life that has been needlessly and senselessly lost by this display of mindless violence."
