On the second level, enter the room with the shotgun in it and two
cases of ammunition. Once you enter through the door, look to the
left. You should see a pole a short distance away from you. Go to it
and go to the other side. Note: Do not go behind; go in front of it.
Then, look towards the corner. You should see a shadow. Jump into
it, then look towards the pole and back up slightly. You should now
be stuck. The only way you can get out is to wait a short time. You
should be able see under the level for a moment. You can now walk
around.