Use the knife to instantly kill anyone you target, no matter where you are! Hold the knife in your hand and hold down the right mouse button to aim at any pedestrian. A red marker will be created on your target. While you are aiming and using the knife, press the left mouse button to instantly kill the target, no matter where you are. You can aim for long distances even through walls.
For the mod to work, you need CLEO Redux. You can download here (clickable).
Installation: move the file to Gameface/Binaries/Win64/CLEO.