I'm sorry you folks lost your beloved animals.
My wife helps run a grooming and boarding facility attached to a veterinary clinic. People will board dogs who can hardly move and owners expect them to be put in "general population" or with other dogs.
She's been doing this 20 years.. there have been many times people bring in an old dog to board and it just dies.. or their first groom so they look good when before they die and their heart explodes.. some have just died on the spot after being walked in.
Or man, when any dog gets a brush out before they go home, finding lumps around their faces and under their legs. It can be heartbreaking working that job.