"Killing becomes murder when (and only when) it is not properly justified, and the justifications are clear: you can use whatever force necessary to protect your own life from a hostile aggressor, or to save the life of an innocent from such imminent, life-threatening danger. The difference between the legal or illegal use of deadly force is really a matter of motive, intent and justification, and these distinctions come straight from the pages of Scripture."
https://coldcasechristianity.com/writings/the-difference-between-killing-and-murdering/