Kill. These precepts are to be taken in their full extent, as prohibiting not only the ultimate act, but every thing which leads to it. Magistrates are authorized to inflict capital punishments. We are allowed also to defend ourselves against an unjust aggressor. But we must never intend to kill him. (Calmet)
The laws will not condemn us, perhaps, if we do; but God sees the heart, and judges. A night thief may be slain, because we know not how far our own lives may be endangered, chap. xxii. 2. (Haydock)