DO NOT INTERACT WITH THE HOSTAGES!
Doing so spawns a few more enemies that roam the area in an APC. Though they don’t count for the trophy, they just make your life difficult. The trophy unlocks when the enemies are dead, rather than when you complete any objectives.
Once you know that, it’s a simple matter of taking your time, picking the baddies off one-by-one. Hitting the power switches at each place will lure one guy from inside each building.
For my play through....
There were 7 in the pool area (Don’t forget to check the roof if you miss any) *Power switch is located through the iron gate to your front-right as you approach the compound after rappelling*
There were 3 roaming outside the front of the clock tower building.
There were 7 in the clock tower building (2 were on the upper floor) *Power Switch is on the far left of the clock tower if you look at the building from the front*
There were 10 in church area (4 inside, 6 outside. There’s one sneaky dude that wanders the wooded area in the SE corner) *Power switch is on the S side of the church*