Capture the dog, and tie it up. Cut it open, and pour vinegar, mixed with salt, into its wounds while it fucking howls and screaches at you. In fact, tape its mouth shut too, and keep rubbing your fingers in his eyes, until they go bright red and start to swell up. Get a load of soil from outside and fill it inside his open-wound, then sew it back up again... I'm not too sure what to do next XD, but make it funny, and force him into a slow and painful death. If you find the owner later on, cut out the dog's teeth and jaw-bones, and send it back to them.
I usually lay down a load of water-proof materials around the room when doing something like this, because it DOES get messy. Very messy. One I do recommend also taping the corners of the material to the top corners of each wall in the room, as otherwise they tend to slip down with all the movement on the ground-sheet.
