The large dog:
Female lab mix, around five years old. She is not spayed and fairly timid, stressed out by certain phrases or actions. In one of her former homes, she was abused. Before she became accustomed to the household, she would often bark and neutralize what she interpreted to be a violent situation (she would bark and take hold of a persons hand/jump up if they seemed to be intending to hit another.) Since, she has become used to her new family, who often wrestle/play fight in jest. She lives with three cats and two other dogs. Sometimes, she would snap at the cats, and she has displayed jealousy, getting in the way so she can eat or get pet first. She has grabbed the cats before, only to be stopped before she could do anything. She has never attempted to hurt the other dogs.
The small dog:
Male Shih Tzu, possibly a mix, over ten years old. He was neutered, but had an old heart and previously lived with a smoker. He was an only dog at first, but then lived with two other dogs before coming to my cousin’s home (he used to belong to their neighbour.) He wasn’t any kind of healthy — he wheezed and coughed a lot, and had a tendency to throw up, though the latter eased off a bit after he moved to a smoker-free home. The female and him never really had any issue with each other, and got along fairly well.
These dogs lived with each other with no problems for a little over a year.
Since my cousin’s family also owns a young, unneutered male, the female was being kept downstairs to be separate from him. The small dog was in the parent’s bedroom, which is mostly closed off from the rest of the basement except for a narrow section that the cats only go through. The owners were going out, so the dogs were kept away from each other in the separate areas of the house. Somehow, the little dog got out of the room, and when the owners arrived at home they found him dead, with blood on him.
Before they left, my cousin said she noticed the large dog acting strange — more timid than usual, and cowering.
There has never been a history of her attacking another animal before, and I don’t think this is a situation where she should be euthanized. I think some advice would be very helpful to settle this matter.