DEVONSHIRE"King's Bridge" is an old name of the market town of Kingsbridge. A quick look in the British Library newspaper archive finds that the story is ripped off verbatim from The Morning Post of Saturday, February 17, 1810, which says it happened "Monday last" (i.e. February 12th 1810), and much the same text was syndicated around regional papers (though it's peculiar that I can't find any sign of it in West Country papers such as Trewman's Flying Post). While children do kill other children on occasion, this story has a bit of an urban myth flavour, especially in its moral message and instant retribution. Also, since all concerned were dead, how is the course of events and motivation known? My immediate thought is - even assuming the basics are true - that the miller ought to be a suspect. We'll never know.
Shocking catastrophe—The following tale of woe should serve as a caution to parents not to permit their children to witness scenes of cruelty of any description whatever:— Mr Hall, a miller at King's Bridge, having employed a butcher to kill some pigs for him, during the absence of the latter to get some refreshment, having left his kinfe behind, four young children, who had been witnessing the operation, agreed to play at kill-pig; the youngest was to play the pig, when one of the others, who acted the part of the butcher, stuck him in the throat and killed him on the spot: the other three alarmed at what they had done, ran into the adjoining mill, and hid themselves under the wheel, which was not working at the time, but was set going almost immediately afterwards, and crushed them all to death!
- Universal Magazine, February 1810, page 166.