Do you have a local SPCA or shelter you could ring to see if they have a large cage trap you could borrow? Our SPCA does which they don't mind lending out. Otherwise a pest control company should have one. At least thats a safe way of catching the dog and if you have it caught the dog ranger...
Sorry about your loss. I would never shoot the dog though - at the end of the day its the owners fault for letting it roam and the dog is only doing what comes natural. I live near a river which is a local dumping ground for unwanted animals now and then, but I have been lucky to catch any dog...