Wow, that's a tough one. I am very sad the dog is gone. But as Jess said, how was the cop supposed to know there was an invisible fence? And they say the dog "charged" at the officer. That makes the dog sound vicious. Was he? And again, how is the officer supposed to know if he's not. He has been on the force for 4 years. That's long enough to know when you should and shouldn't use your gun, IMO. Did he use it correctly in this situation? I don't know.
Like I said, it's a sad story no matter what.

RIP Callaway