DEUT944 The Talmud teaches: "From where do we know that if someone pursues another [that is, an innocent person] to kill him that the pursued should be saved at the cost of the pursuer's life? The Bible teaches, 'Do not stand idly by while your brother's blood is shed'" (Sanhedrin 73a). In other words, if we have great strength, fighting ability, or possess a weapon, we should use it to save an endangered person's life even if it means killing the pursuer. [When a person sees a pursuer pursuing a colleague to kill him… and he has the potential to save the pursued from the pursuer and does not do so... such a person violates two negative commandments, 'You must show him [in this case, the pursuer] no pity' [this verse], and 'Do not stand by while your brother's blood is shed'" (Maimonides," Laws of Murder and Preservation of Life" 1:15). If the threat can be averted by injuring the assailant in the leg or arm, we should do so. Jewish law regards it as murder if one intentionally kills the assailants (See Sanhedrin 74a and Maimonides, "Laws of Murder and Preservation of Life" 1:13). However, if the pursuer seems intent on killing or seriously hurting his victim, then you should stop the attacker by any means necessary, including killing. Your goal should be to use the minimum force necessary to prevent a criminal act. However, when the pursuer's intent cannot be ascertained, the primary goal, according to Jewish law, it is to protect the pursued (see Sefer HaChinnuch, commandment 600). ... Similarly, when police confront an assailant who has a weapon and is threatening them, they should try to preserve his life by disabling him. But they are not required to put their own lives at risk. In the words of an ancient biblical expression, damo b'rosho ("his blood is on his head"; see, for example, Joshua 2:19 and Ezekiel 33:4).