Use the item box to put away the Hex Crank and whatever big weapon you have. You won't need it. Now find the only door, and enter it. Keep going and Lisa appears in the direction you head first, so ...

When you go down the ladder, there'll be a door next to you. Don't go in yet. Keep going forward. Put away your Square Crank in the item box; you won't need it again. Take your Shotgun or Grenade ...