Very early in the game, after you wake up in prison and retrieve the explosive, you will soon enter a room with a waypoint that says "Door Control". There are three guards here. Quickly activate the door control and run into the next room that opens to lure the two guards there after you.
Note: there are also two guards in the room prior to this that you can alert instead if that is easier.
Either way, once all five guards are in combat with you, simply kill them and, achievement unlocked.