You can unlock this achievement on Chapter 4, Checkpoint 8.
You can use Free Aim, Soft Lock or Hard Lock.
As you leave Max's apartment (There's a Badge clue, and golden gun part in the apartment), as you exit you'll see three enemies you need to take out who are down the hallway, take them out from Max's apartment, then as leave the apartment you see green lasers coming through the windows on the left, these are the guys you need to kill.
This video was done on the hardest setting using Free Aim
http://game-play.tv/video/XRRA2D41WKX9/Max-Payne-3-That-Old-...