Silence, Fool! Trophy
Kill a guard ringing a bell.
This can be done wherever a warehouse is. Warehouses are at farms and have a restricted area around them (shown with red color on the map).
Once you enter the restricted area you should see the alarm bell on your HUD. Get noticed by an enemy and wait for him to ring the bell. Quickly kill him with a melee attack after he starts ringing the bell to unlock this trophy. You can also do this at warehouses that have already been looted.
Here is a video of this trophy from PowerPyx: