Hi Strezzle. Going back to this dog, what breed of dog is it?
You must contact the RSPCA also regarding this dog as it's a danger and you say that you have children. Explain your concerns for both your remaining cats and also your children as sometimes the RSPCA have more power than the police where dangerous, out of control dogs are concerned. Get your neighbours together and get their support because if this dog is a nuisance environmentally i.e barking all the time if left leashed outside you can raise this with the council, all this will help you if the case goes to court.
I am not an anti dog person nor want to see any animal hurt or euthanizied, I love all animals but the owners of this dog need to be held responsible for the actions of their dog especially when an attack and fatality has happened whether it be to another animal or human.
Let us know what happens......