Alright so I guess the question as Tilt has framed it is:
"Is it never justified to kill one person to save a another?"
My view is one cannot go wrong, by never intentionally killing another human.
edit: nevermind, I don't want to encourage anyone to even attempt to use the Buddha's words to justify killing. Shouldn't be done.
"When one thing is practiced & pursued, ignorance is abandoned, clear knowing arises, the conceit 'I am' is abandoned, latent tendencies are uprooted, fetters are abandoned. Which one thing? Mindfulness immersed in the body." -AN 1.230