: go inside the last building, go to the last floor (top) and head out to face the center of this area. I don't remember if there's a Carbine or a sniper-covenant rifle. Both hunters just will stare at you for a moment, then turn around and start walking away. When they do this, shoot one of them in the back (their weakest spot along with their "abdominals"). They will turn around again to face you, don't do anything now -they'll probably shoot back. Wait for them to turn around and expose their backs again, shoot them...etc.
Always shoot the same hunter to kill him before you run out of ammo; when you kill it, you can go downstairs and take the hunter left any way you want it (shotgun and brute shot are good choices)