Sanhedrin 74 - Use of Lesser Force

Rabbi Yonathan ben Shaul said, "If a someone was pursuing a victim with the intent of killing him, and it was possible to save the intended victim by disabling one of the pursuer's limbs, and the rescuer did not save the victim through those means, but instead killed the pursuer, the rescuer is put to the death on the account of killing the pursuer." Whether the rescuer is actually executed by the courts for killing the pursuer, or whether he is subject to death by the hands of Heaven - is a subject of disagreement between later authorities.

If someone being pursued broke items of the pursuer, he is exempt from paying, but if he broke items belonging to any other person, he is liable. However, if the rescuer was chasing the pursuer to prevent him from committing murder and broke vessels of any party, he is always exempt, because otherwise nobody would be saving his fellow from the pursuer.

Art: Emile Friant - The Fight