In which someone actually does. "You're going down," much like "This time it's personal" or "Nobody messes with a [insert gender, ethnicity, or combination] and lives to talk about it," are things you say in your head when you're thinking about how you will stick it to someone. They're placeholders—not things you actually say during the sticking because they are hackneyed, unspecific, and inaccurate.
Nevertheless, on August 2, a man was driving west on I-40 with a friend and her 10-year-old daughter when he looked in his rearview mirror and saw his parents-in-law and his estranged wife following him in another. He had reason to be nervous about this, it seems, because he had recently taken restraining orders against the wife and the father-in-law. So, to try and get away, he got off the freeway at Lovell Road and pulled into a gas station. When the car followed him there, he got out and walked into the gas station, telling his companions to stay in the car and lock the doors, which they did. The wife, carrying a video camera, came up to the car and started banging on the door. When she saw that her husband wasn't in it, she went into the store to find him, which she did, and for no apparent reason, began taping him. Then, her moment came. The man: "Please stop stalking me. I'm going to have to call the police." The woman: "You're going down." Then, she put down the camera and walked back to her parents' car. At this point, we'd like to imagine that here commenced a high-five-athon that didn't stop until the fifth or sixth viewing of the tape that night.