WATCH THE VIDEO!
Info Prior to Watching: This achievement can be unlocked on the mission "night shift" at the very beginning of the campaign. The lights can be seen in the parking lot across the street from your sniper position. Account for the left to right swinging motion of the lights and aim slightly above the visible light (differs depending on the difficulty mode). Use the video as a reference as where to place your sniper crosshairs and use the left-stick to stabilize your shots in this position. If you miss a shot reload the checkpoint. Also I found it easier if I went for the back shots first because they are the hardest to make so if you miss them you dont have to keep remaking the easy shots.