Murder is the desecration of the image of God. However, there are circumstances where the taking of life is lawful: self-defense, capital punishment by the state, and state-declared war.
God told Abel that the attitude that led to his murder of his brother Cain was sinful, Genesis 4. Jesus also says that anger and hatred are sinful, just like murder, Matthew 5. We ought also to avoid actions and attitudes that damage ourselves or others particularly because the body is the temple of the Holy Spirit.