Ghost At Work

I have been working at a University in New Jersey for 8 years. The building that I work in was built in 1999 and is a relatively modern building. Ever since I first started to work there, when I would use the ladies room I would hear someone moving in the stall next to mine. I would look down and never see feet or anyone else in the bathroom. This has gone on for the entire time that I have been working there and I have heard other co-workers tell me that they've heard the same sounds. I have stopped using the bathroom in the hallway and now use one inside of the office.

About two years ago they needed to add another office, so they broke through a wall and expanded the space that we were already in. My new office cubicle is right next to a fire door. My boss likes to leave the fire door open so that she can take a short cut to the haunted ladies room. She used to leave it propped open all day long, but one day one of the girls complained and asked that my boss keep it shut.

Once we started to keep the fire door closed, I began to hear knocking. Whenever I would get up to open the fire door there would be no one in the hallway. 2 minutes later the knocking would come again and my boss would open the door and no one would be standing there. You have to understand that there's a very long hallway and our fire door is at the end of it, so there is no way that someone could disappear fast enough to not be seen after knocking and having the door opened immediately.

Sometimes my boss still leaves the door open and when she does I can hear someone moving around in the office behind me (that is my other boss's office) I will hear papers moving and the chair rolling and then he will not be in there. This has been happening for so long now that I really feel like the ghost or entity or whatever it is likes the fire door open so that it can move about the area freely, from the bathroom, to the long hallway, to my boss's office etc. When the door is shut it knocks to be let in.

Just today I heard something tap my desk and tap the papers on my desk like someone was standing there with a pen. I knew what it was immediately. I don't think it's harmful, just mischievous, but I find the thing very strange since the building isn't very old and I am not the only one who hears these things so I also know that I am not crazy.

Well, that is my story. Does anyone have any idea what it is or what it might be? Why it stays in the general area of the ladies room and the back office that got added on?

Thank you.