My ex-spouse’s step-mother died from an acute case of not being alive anymore. She was in physically good health, good heart/blood pressure, mentally sharp, was a distance swimmer, ran, smoked occasionally (like 1-2 cigarettes a day), and was in her mid-60s. She collapsed in a supermarket and was dead before any help could arrive. The autopsy couldn’t find any cause of death; no ruptured aneurysm, no stroke, no heart attack or heart issues at all, no drug interactions, nothing. She just… stopped being alive.

Shit happens sometimes, and there’s not always an obvious cause.