The poor old pet. Ash is our first dog, so we haven’t been through declining years with a dog yet: only catz, and the current ones are both under 5 years old.
The 20-year-old miniature dachshund simply went to sleep and didn't wake up, My stepfather found him the next morning. (We kids loved him, but he was not an affectionate dog.)
The 14-year-old coyote-shepherd mix was barely about to walk, incontinent and in much pain, but the Evening Before he managed to escape from the yard, walk a very long block, right into traffic on the arterial there. He was very much family, and is remembered as such.