When one has no reason to contemplate death because their life is not at risk, it is hard to determine if they will fear death when the time comes. Generally speaking, people fear what they do not understand. If one does not understand why their life is endangered or must be sacrificed it is likely that they will fear death. If a person has not achieved their goals in life, contributed in some way to the world or impacted the life of another person, they will not be so willing to give their life away. People like to believe that when they are sacrificing something, it is for the good of others or something else. It is not likely that someone will willingly give up their own life or face death willingly for no specific purpose.
If someone were to tell me that my life was in danger and there was a possibility that I would die, I would be afraid. I know that I have not experienced enough to satisfy my reason for being on Earth. I still need time to make mistakes, to grow, to choose who I want to be for the rest of my life. Until I have achieved my goals and made my mark on the world I will fear death. I know not of what comes after death and because it is unlikely that I will ever know (at least while I am alive), I have no reason to look forward to death and embrace it.
People that don't fear death have either satisfied their personal reasons for being on Earth or simply don't wish to be a part of the world anymore because there might be a better place after death. Most likely people that don't fear death are quite old and have experienced a lot in their lifetime, terminally ill, severely depressed, suicidal or a combination of the few. If they don't fear death they must believe that life has nothing more to offer them, and by dying, they will not be missing out on anything. Personally I do not know anyone that does not fear death, I can only suggest the kinds of people that might not fear it.