I personally know of a situation where an armed person held a couple hostage, and police responded to the incident. They asked to use our building to station a sharpshooter on the roof. The armed person was overwhelmingly outgunned, but instead of killing him they took him down with a non-lethal beanbag round. It's not necessary to kill even in extreme situations.

There are a couple of prevailing attitudes within the policing community and community at large that lead to officer involved shootings. One is the attitude of fear: Kill or be killed is the idea. Two cops are handed the mandate by the public to be the judge, jury, and executioner; The motivation being it's less mess and time consuming (pure selfishness).