I'm so very sorry for your loss of Dear sweet Gizmo.What a horrible thing that a dog could do to such a great Creature.Cats are the greatest creature on this earth(I believe anyway)and whichever dog did this (I believe should be indoors or on a leash with a PERSON on the other end of it and NOT tied up)
Accually if it were my cat I'd probably bring the person to court to have the dog put down and NOW I'm going to get a lot of people mad at me at Pettalk but so be it.
Poor Gizmo.Again I am sorry