Incompetents couldn't do it with a good ol fashioned throat slashing so they did it with a chainsaw.... in front of a bunch of kids.
While the dog needed to die, a chainsaw (and the kids) made what should have been a humane enactment of frontier justice into a gory scene best left to Hollywood.
Hard to agree with the sentence of 8 years, but really, a chainsaw.... in front of a bunch of children?
The custom used to be (maybe still is) that you call the sheriff and he handles the problem with a gunshot or calls some other authority. Makes sense.