Pardon my pushback, but wouldn't it be easier to just answer: the mouse has died. I know that's not religious and everyone has their own views on the soul, but: do we need to ease feelings about a dead mouse? I see the death of wild animals as good opportunities to teach children, so they're more prepared for the death of humans they know or their pets.
Like almost everything in parenting, it’s more complicated than you would first think. My toddler knows our elderly dog went to the doctor and died because she was sick. But when he asks ‘why’ I have to clarify that: she was sick but not the same way he gets a cold; that the doctor tries to make people feel better too; that she’s not dead in the way replaceable batteries die; and that her grandparents won’t die when they get a cold even though they also get sick.
I avoided the rookie mistake of telling him that the dog went ‘to sleep’ (because then he might worry that he’ll die if he goes to sleep too). But there were a dozen other considerations that I also had to make, up to the point of changing our wording when batteries or electronics ‘die’ from now on.
I think that's the point that GP is making -- they were contrasting a straightforward approach to their mother's more euphemistic explanation, which was unsatisfying to them as a child.
