Or perhaps, hear me out here, we could dedicate an entire field of science to understanding human biology, and train many people in this subject as professionals. They will be qualified to, among other things, examine a patient and determine objectively that they are deceased with no chance of revival. They can then verbally communicate this fact, or in other words, "pronounce" that the patient is dead.
idk I'm just spitballing here.
I find it odd that natural disaster isn't on your list considering it's by far the most realistic scenario. Hell, it's already happening.
I guess the word "natural" isn't very accurate for a climate disaster, but still, it's not on your list.