Our Newfoundland pup is a member of our family as sure as my two legged daughter is....although when she was in high school I thought some of her boyfriends were mongrels. They didn't last very long.
My years of teaching psychology and the interviews I've done with folks in the profiling field suggest to me that people who do these kinds of things are on the road to being serial killers. When you have a chance to nip evil "in the bud" so to speak; society should do so, IMHO. Put this guy to sleep. It's the only humane thing to do.