I had to put down my favorite dog a few years ago - he was a beautiful blue-eyed husky. Smartest, most vociferious dog I ever had.
But he liked to hunt, and his choice of game was a problem. Horses, sheep, and the neighbor's kid's pet goats.
After he got the goats, he got loose one day, and my neighbor came running out of her house, grabbed up he kids, and ran terrified for the safety of her house.
I thought, "That dog would never touch those kids. But I would not live in fear like that, and neither shall she."
So I put the dog down.