Here is my guide from my channel, Toslow Gaming. Load up the chapter, "Return to Heroes Plaza". Use a tear to pick up a sniper from the ammunition crate. Make you way to the Sky-Line (the one between Soldier's field and Heroes Hall). If you have it, Throttle Control Gear would be useful at this point. Slow down, and snipe off the heads of the enemies who are to your right. If you don't get five headshots, their are more policemen if you continue further into the Sky-Line. Make sure you put HD.