Bob and Alice are having a fairly mundane conversation. Bob stares absentmindedly out the window, and Alice is walking around the room behind him. Without changing the tone of her voice or the subject of the conversation, Alice picks up a gun, walks up to Bob and shoots him. This trope could be used for several reasons. To spice up a boring conversation, to establish a creepily detached mood, to reveal a traitor, to portray a character as deranged, overly methodical, a dog-kicker, or to show they long since crossed the Moral Event Horizon. Bonus Points if the victim is Killed Mid-Sentence.