The mishnah at the top of Sanhedrin 73a defines sinners who may be killed by anyone if that is what it takes to prevent the sin. Such a sinner is called a "rodef". This is Wikipedia's translation of the mishnah:
And these are the ones whom one must save even with their lives [i. e., killing the wrongdoer]: one who pursues his fellow to kill him [rodef achar chavero le-horgo], and after a male or a betrothed maiden [to rape them]; but one who pursues an animal, or desecrates the Sabbath, or commits idolatry are not saved with their lives.
One aspect of the law that is not explicit in the mishnah is that a rodef doesn't have to have malicious intent. A rodef just has to be an immediate danger to someone's life. Whether the rodef intends to be such a danger is irrelevant. This is one of the reasons that abortion is allowed to save a pregnant woman's life.
Another example that is very relevant right now is the 2.2 million Gazans who are being used by Hamas as human shields. Zahal is free to kill anyone it needs to in order to achieve its military objectives.
