send the owner a rock by mail fro another city. wrap a note with a rubber band...say "this rock will serve you notice that the next rock will have poison and a cookie for your barking dog next time"
Let the owner live in fear...
I had a neighbor once who told me that "sometimes you have to be crazier than them to stop them"
Let them drive themselves crazy trying to figure out who is going to kill or injure their dogs. Play dumb...make no indication of your intentions or actions...
BTW, I don't care to hear from all the bleeding hearts on how cruel or mean...blah, blah,
...save that for yourselves that bring upon their just "reward"