This will happen in the final section of Belly of the Beast. You will come to an area where you are overlooking a line up of troops and an officer walking back and forth. What I did was move down the stairs and use the welrod on the first two guys you see after getting off the steps. The officer may come over to investigate, use the welrod on him. Next, sabotage the generator to create the sniper muffle noise. Move around the front of the truck by the generator and there is a guy with his back to you that can be stealth killed. Move over to the right of the generator, line up headshot with sniper on the first guy in the row. Wait until the noise icon appears and take the shot for multikill.
Now you can take everything out. Shoot all the 'red' objects to destroy the area. A counter will appear to show you how much has been destroyed. When it hits 100% trophy will pop. There is a glitch that some people, myself included, had happen. If you hit 100% destruction and no trophy, walk past the first truck back towards the rest of the level and walk off the cliff. When you respawn the trophy TNT will pop.