here's the important part....
(a) A person is justified in using physical force upon another person in order to defend himself or herself or a third person from what he or she reasonably believes to be the use or imminent use of unlawful physical force by that other person, and he or she may use a degree of force which he or she reasonably believes to be necessary for the purpose. A person may use deadly physical force, and is legally presumed to be justified in using deadly physical force in self-defense or the defense of another person pursuant to subdivision (4), if the person reasonably believes that another person is:
If you go to court, you have to be able to convince a judge and/or jury WHY you believe the above. A target shooting at you or shooting at a second party can be cut and dry, but those questionable not so clear facts, the sweaty palm kind, they're the ones that come down to what you can prove... not the truth.
Its good to know your state guide lines on the use of deadly force, i would try to get training so not only would i know it... but understand it. If someone is outside of LE try to take a course/tutor/classroom instructions.