Insanity's Edge

You are Sergeant Shaun Rumsey, a marine on a UAC base on earth that was recently attack by the forces of hell, after finding a large hell portal in the mines. Marines fought bravley, but were outnumberded and slaughtered. As far as you know, you are the only one left on this base, and it is amazing you are still alive. Maybe you have better skills than you first thought. You see a shotgun in front of you, and hope that no demons will come teleporting in once you pick it up.