The ethics of a police robot bomb

Dallas Police face questions this morning over the method used to kill the sniper in last week's officer ambush. Police sent a robot armed with explosives to kill the gunman. Robots in the past have stopped a lot of dangerous situations. They can do pretty much anything a person can do: go upstairs, communicate via speakers, and use cameras to explore a scene, and at least one has been deployed to spray tear gas to subdue a suspect. But using a robot to kill?