Officers should only fire their weapon when there is absolutely ZERO other options and people's lives are in danger. And if the situation reaches such a critical mass, then they should shoot to the finish. The last thing you want to do is try and shoot an arm and miss and wound an innocent bystander/hostage. Or shoot a non-fatal wound and allow the perpetrator to start shooting back. If there is no other option but to shoot, you shoot to the finish.