Also the question is incorrect. There isn't an exact time when someone dies.
Given that we don't really have a precise definition of "alive", it should not be surprising that we are unable to tell the precise moment a person dies.
Relevant: https://youtu.be/ibpdNqrtar0
Given that we don't really have a precise definition of "alive", it should not be surprising that we are unable to tell the precise moment a person dies.