in the u.s., the same situation (armed aggressor with hostage) would bring out the entire police cavalry. if the hostage taker is in public view and his head is exposed to sniper scopes, he would be taken out by a triangulation of police sharpshooters with very powerful rifles. if sniping is not possible, the wait is too long, negotiations or attempts at negotiation fail, and the swat team has to move in, they will overkill by expending as many rounds as they possibly can without harming the hostage.
Wah, another bullshitter dirty harry. I can guarantee u that if a hostage taker was armed with only a knife, no police sharpshooter will "take him out" with a head shot. There will be hell to pay in a public inquiry. The only reason they will start shooting is if the hostage taker kills a hostage. Than all bets are off. There is a famous video of a police sharpshooter shooting the gun out of the hand of a crazy man. This crazy guy had a loaded pistol, and infinitely more dangerous situation than a knife. he could have shot at and kill a police officer quite easily. u can see the police are trying to talk to him, but they resist shooting him, dispite the fact he could have at least squeeze one shot off at the police. Finally, a police sniper shot the gun out of his hand. Not shoot him in the head, hand or leg. But shot the gun. The worse he had was a sprained hand. This guy lived. I defy u cowboys to say this was the wrong outcome.
http://www.youtube.com/watch?v=H1EESuJMSkM