So I've now seen, and read, two different ways to do this. Both are in scene 10, Graveyard Shift. The first way, and perhaps easiest, is (this is taken from the comment portion of the video done by Secular Stoner) "Once you clear the first area of Skinz an open the gate, grab the save point. The next room after this save point will have five hunters in it. You need to kill the one hunter with the pistol who shoots at you straight away an the two hunters that rush you with baseball bats. After this the two other hunters will be standing behind a wall of boxes in a line making it extremely easy to get this trophy." And here is the video:
The second is at the beginning of the scene. You run directly forward and up the stairs, carefully. You'll see one guy standing guard. You shoot him in the head, and then attempt to line up the two people running up. If there's not two people running towards you from the right of the man you just killed, reload the level. Here is a video demonstrating this, done by Platinum Hunter: