It is a very diffucult choice. In any case one must employ some kind of logical reasoning in a situation which is very stressful. The office needs to access the situation, how much of a threat the suspect is, do they look like a terrorist, what are they saying, are they near other people who could be in danger. They must mkake they decision in a split second and it is inevitable that there will be mistakes.

I dread to think how the family of that guy who was shot in London feel, I also dread to think how the police office feels about making the wrong call. There are victims on both sides.