--From the janitors point of view--
It was the end of the shift and everyone from the night shift was preparing to go home and relax. No one had spilt or dropped anything all night, which ment no cleaning. The janitor was preparing to go on a lunch break when he saw the door to his closet open. He walked over shut the door, not hearing any voices inside and not seeing any light coming from inside the presumed that no one was in there, so he locked the door, placed the keys in his pocket and went for his lunch.