After you are ordered to secure the ground floor of the starting area, go to 
the hole in the wall where the gun emplacements are located. Move north 
through the door to enter a narrow flooded area. Go to the end to find a 
Kilroy on the wall.
After you are given the order to clear the top floor of the warehouse, there 
will be an intermission sequence showing you ascending in an elevator. 
Afterwards, go to the doorway to the west. Immediately turn right to face 
north after you enter the doorway. The Kilroy is on the wall.