This is a decision based trophy unlocked fairly early in chapter 9.
There will be two people hanging from a sign. You will be surrounded by snipers and have to choose whether to kill the two people or attack the snipers and start a firefight.
For this trophy, attack the snipers. Duck behind the car to the right and snipe the sniper closest to you over the car's roof. If you try to do this out in the open on anything above easy, you'll most likely be mowed down.
This trophy will not pop until the next checkpoint so you'll have to play through a second time for the other choice.