If you want a machine gun and shotgun on the 1st level you must get to the checkpoint where the guard 1st gives you the pistol armour flashlight etc after hell has broken loose. When your using the computer to open the security door underneath the button should be a small panel. Click it then click unlock door 1. this will allow you to get the machine guns and shotgun you saw the 1st time which apart from the shotgun you wouldn't be able to get laster in the game. Getting these weapons will spawn 2 imps but with the new guns its easy.