You guys are all off of the highway, in the middle of a grassland, but you know that disabling the car in front of the stampede would remove quite a lot of cars from the equation. You aim carefully, taking into account the bullet drop from distance, the wind speed, the circular movement of the drone, the updrafts from the sun, and the slipstream created by the drone as it flies through the air. Taking all this into account, you fire the largest shot you have, which is a 60 caliper rifle shot, way ahead of the drone, and slightly higher than the target, so the bullet arcs through the air, and smacks into the front camera of the drone. The force of the shot rips the camera straight off of the drone and it tumbles gracefully through the air. The moment the bullet hits, all the cars swerve crazily as they no longer know where they are going, but then on of the drone's 3 other cameras takes over and the cars get back on track. But that was when the falling camera landed straight into the tire of the lead car, causing that wheel to lock up and the car to spin out. The sudden movement gave the following cars no time to get out of the way, and a giant crash in the middle of the stampede ensues. The 6 cars on the wings of the stampede ignore the crash and continue onward, but at least the 6 in the middle are either disabled, or destroyed. Furthermore, the intense heat of the car crash seemed to distract the heat-seeking missile of the drone, and it slammed straight into the epicenter of the crash, turning what used to be cars into scrap metal. The drone lets off another missile, this time, a computer targeted one, and the 6 remaining cars, traveling at highway speeds, will barrel into you and your group in another 10 seconds at most.