Anything with preydrive is going to go after a frickin' Yorkie. I'd go after a Yorkie myself just on principle.
I would write a letter to the editor, definitely, and discuss prey drive and the animals who have it. Because if this dog has been killing other small animals it definitely sounds like prey drive. Also, screw citing the owner, I think the guy who was taking care of the dog is the one that needs a citation as he obviously has no idea how to properly care for a dog, especially one with high prey drive.
"All changes, even the most longed for, have their melancholy; for what we leave behind us is a part of ourselves; we must die to one life before we can enter another." -Anatole France