I've learned that てしまう is used for either complete or unintentional actions. In this example, they're using it with the verb 死ぬ (to die). I'm confused because I feel like none of these are applicable. Either:
- He died completely. But how can you die "not completely"?
- He died unintentionally. But when do you ever die intentionally (other than suicide). This would mean we have to use てしまう every time we use 死ぬ, because most of the time people die unintentionally.
My guess is that it's reinforcing point #2 and gives a certain nuance. Could someone elaborate on this?