The Bible says , when asked to choose between Life and Death, choose Life.
If you shoot someone that is threatening your life or property, it is called Self Defense.
The 6th Command in most Christian Bibles says , "Thou shat not kill". But scholars say that is and incorrect translation of the original meaning of the Greek/Hebrew words. It should read, "Thou shalt do no MURDER."
It is not a sin to kill someone in self defense, or in the service to protect America in war, or as a police officer in the act of duty. It is a sin to murder someone out of anger, intentional gain, hate, etc.