This Seeking Tech tutorial will explain how you can get the Like He Just Doesn’t Care trophy and achievement.
This will unlock when you “hold up an enemy.”
In order to do so, sneak behind your enemy. Keep in mind that the enemy may hear your footsteps, so you should use the Stalking Mode by holding L1 to walk slowly and quiet down your steps.
Once you get close, aim your weapon at the enemy to hold him up and unlock this trophy/achievement. Check out the video walkthrough below if you need more help: