Question

what happens to body when a person is decapitated

Answer 1

First of all, unlike in movies, some commonly accepted methods of causing “instantaneous death” are actually not as instantaneous as you think. For example, shooting someone’s heart makes the heart stop, that is true. However, we know that without air, a human being can survive for over 3 minutes. Since that is because the human body continues to absorb the oxygen in the blood and leftover oxygen in the lungs continue to be carried away if the heart is still beating, the time should be a couple times less, say, 1 minute, before the brain of the shot person stops functioning. The same should be true with decapitation.