Lets imagine that you are a special force soldier and your superior, order you to exterminate some target that is somewhere in the world. You know where this person is living, but you don't know any other details. In the perspective that you going to finish the job, not mater what it is needed, you will probably enter some house and try to find this person, while many other persons can be there and therefor, you can kill many innocent people.
When someone question an order, it is not denying to accomplish the request. It is in fact, demonstrating that the information about the target is needed to be more accurate, resulting in being fair. If you don't care about being fair, you can drop a nuclear bomb in the city, kill some billions and you are "almost sure" that, that single target is dead too. But you kill many more than one single person. (like the American did against Japan somewhere in Time)
If you know more details about the life of this target, what he likes or dislikes, you can get the target without using any kind of violence against many or even against the target it self. This can take you extra time, while you have time, since life is about time, you may need to learn the language of this person, the habits, his work, his friends and many other details that can be useful in the "Criminal perspective" (even if in your Legal case, your activity will not be seen as illegal, because you work for the Government ).
All the information that the government or your superior can give you about this person, will help you to accomplish the request while being accurate in what approach you going to use to exterminate the target that is a problem for your government. Even then, you can question why this person is a problem to the government, and based on that information, chose to deny to accomplish that request, because You are FREE to make a choice. Imagine that the answer that your superior give you is "we want this person dead because he defends human right". You are a human too and defending human rights, should not be a problem to any government, because governments are a mechanism to guarantee that human rights exist. (so it would be a contradiction) Then you can wish to know more, since the answer that your superior gave you, doesn't make any sense. (by logic)
In your research to understand the case, you can find for example that in fact this order is not by government will, but by your superior will to get an extra money from some criminal group and your superior by that condition, it is criminal too. If you accept to take this action without thinking and without questioning, you will become a criminal too. So, please use Your Brain the best you can, because Society was built using the brain, your clothes too, your guns too, you tools too, your training too, the laws of your country too, and everything that humanity did create in history, too.
Note: Is known that the two soldiers that drop the Atomic Bomb had no idea of what they were about to do. One of them get mad and the other become a priest (by the illusion that God will forgive him for his Sins)