Good question.
Some years ago the Chattanooga SWAT responded to a call near where I live (more than 30 miles from Chattanooga proper) because some geezer was mad a the world and had "barricaded" himself in his trailer. He had no hostages and was in danger of hurting no one but himself. The local Sheriff's Department asked the 'Nooga SWAT for help. All they really needed to do was wait the guy out. The SWAT team arrived, accessed the situation and shot the man dead in his own home. Many questions followed, not the least of which was why the Chattanooga SWAT team responded to a non-threat in a community 30+ miles away when the Chattanooga Fire Department never responds to structure fires in this area. The answer to that one was simple. When you are a Chattanooga Fireman responding to fires you don't get to kill people in cold blood......
So the worst thing he likely would have done was kill himself and they eliminated the threat by....killing him. I take it they had to kill him to save him?