heartbreaking story. I probably would have had the dog wakened so I could cry over it for awhile. I am so attached to my animals and when I lose one I lose my mind for awhile. I worked for years in mental health and also fostered many animals. I happened to have a foster kitten that I found in the bushes in the back yard. Very young. Very sick, with upper respiratory and drippy eyes etc. I nursed him to good health and he was thriving. I was just getting ready to re-home him when he took a bad turn. Throwing up, getting skinny, we went to the emergency animal clinic like 3 times in a week, I was just writing checks left and right because once I was in I was IN. He started to need hydrating, I would drop him on my way to work, pick him up on the way back. They called me while I was at work and told me it was not any of the things they had thought but was in fact Panleukopenia (feline distemper) and he was gasping for breath. I agreed to let them put him down and then had a meltdown 5 minutes before a treatment team meeting that included the director and the psychiatrist at a clinic. Of course I sobbed through the whole meeting and end result was they sent me to "supervision" (where you go if they feel you might not be doing good because in mental health it is imperative that you do no harm) in other words they thought I was having a nervous breakdown. Even though I kept saying "I had to have a kitten euthanized" nobody understood and even said things to me like "it is just a cat, nobody acts this way over a cat."
I later realized this is why the tiny kitten was abandoned in the woods and no mother was around. The mother cat will do that if she suspects one is ill to keep it from getting the others sick.
I've had my meltdowns over pets before. It's always a terrible loss. You just try and make the best decisions you can, sometimes they're the decisions that are tougher on you. With all the love and joy they bring into our lives they earned our tears as they move on to wherever cats and dogs go for eternal love.