Our county policy is that "dogs at large"  can be shot if harassing/attacking/killing livestock.  We're supposed to contact animal control after such an event happens so they can make a report and come pick up the animal.  
My neighbor's dog got into my chickens last week and killed 6.  Knowing whose dog it was and that it hadn't done this to ours before (it had killed some of their own), we attempted to catch the dog to take it back to them.  Dog tried to bite us--owners were not home--dog then proceded to chase cats--so bye-bye doggie.
Called the sherriff out to make the report (it was after hours).  The sherriff was quite snotty with us over what we had done and why couldn't we had done something else, blah, blah, blah....
(The neighbors actually ended up being not bad in the end)
We've also had other dogs who've haulded back to their owners (alive), told them their dog was chasing our chickens, and have had the owners be very crappy to us (like it our fault their dog runs loose?)
So that's why, from now own, we will most likely go SSS