As the description is self explanatory it's also glitched. Good work around is wait until its your last trophy and copy your save to flash drive if you wish to keep them. Next delete everything including the application, eject, reload and play up to chapter 2. You will come to a part where you see people transform silent kill the one infront of you forget the guy along the side of house. You will come across an autosave when your close to cart. There will be enemy just infront of a fire, you want to sneak left go along giant hay stack, jump fence and silent kill. Wait a few seconds and reload autosave. Rinse and repeat. My trophy unlocked on tenth kill FYI, i think i wasnt waiting long enough between kills to reload. Hope this helps.