system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do people die instantly when a bullet passes through their heart?

I just randomly thought about this, but why do people die instantly when a bullet passes through their heart if they can maintain consciousness for around 15 seconds and stay alive for about 5 minutes without oxygen? Feel free to correct me if I am wrong about anything.
gpt
Your blood pressure essentially drops to zero and you black out. Technically there is still some brain activity going on at this point, but considering you will be unable to maintain consciousness and you will die shortly after, its fair to say its instant death.