I here people say you don't fall asleep if you may have a concussion because you may die and what i want to know is how does it physically kill you?

Not true: Of course, at some point everyone who has a concussion goes to sleep; and obviously the vast, vast majority do not die. What we are trying to watch out for in all people who have had a head injury, is a declining mental status which could be a sign of a more serious injury than a concussion such as a head bleed, and that could potentially kill you.