Wear the Spider camouflage and black face paint. When the battle starts, run straight to the end of the row and do a left U-turn down the next row. However, stop at the beginning of that row. You can get a single shot off at him with the shotgun. Then, run to the main door. Once at the door, crouch down and he will eventually walk by. You can shoot him and he will not see you if you have the correct camouflage and your stamina level is high enough. He stops at two places in front of the door where he can easily be shot. He will fly off after every shot and return where you can shoot him again until he dies. Sitting by the door allows you to defeat him without any damage to Snake.