system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does a gunshot to the head cause immediate death?

This sounds very obvious, I know. I assume it doesn’t immediately stop the heart, and people can still survive even while being “brain dead”. So what exactly happens in the body to cause immediate death once a bullet enters the brain?
gpt
The bullet will have multiple effects. 

The first will be a high pressure wave. Water, what you are primarily made of, does not compress. So the force of the impact will cause powerful waves of force inside the skull. These force waves will shred neural connections. 

Then you have the physical damage of the projectile passing through the brain tissue. It is probable the bullet (or bullet fragments) will be tumbling - shredding tissue as it passes. 

Then you have the exit. The pressure wave will open a hole at the exit many times larger than the entry wound. Out of this hole will be thrown large quantities of destroyed brain tissue.

Your consciousness most likely ended at the moment the pressure wave scrambled your brain. Since you have no awareness after that point it really doesn't matter when your heart stops or other tissues die. You effectively no longer exist.