Mystery!

I don't know if you believe in this kind of thing or not, but hear me out.

I've worked evenings at a gas station since October, and have sensed some creepy things in that time. Most of the time I'll just hear one of the bathroom doors close, when I clearly did not see the door in question open and there is no one anywhere near the store. Once I was cleaning a shelf and felt a cold breeze come up behind my left shoulder, and when I turned around the only person I saw was my coworker giving me a "you're kinda crazy" look from the other side of the store.

And then I worked last night. I was on bathroom cleaning duty. Most of my coworkers will prop the door open while cleaning, but I find it's easier to shut and lock the door. I don't know, I guess I like avoiding people sometimes. Anyway, I was in the women's room and wiping the counter down when I heard the door handle jiggle, followed by a knock. I called "just a minute!" as best as I could through my impending laryngitis as the handle jiggled one last time.
Upon exiting the bathroom, my coworker asked what I had yelled. I repeated myself, explaining that someone had knocked on the door. He looked at me as if I had grown antlers and said that no one had been in the store.

Um. That's kinda creepy.

Later he started telling me about how he's heard the door-closing sounds before too, in addition to various creaking noises that can be likened to someone walking on stairs (of which the store has exactly zero), and that it all gets creepier the later you're in the store (i.e. when it was still open 24 hours). We spent the rest of the shift pointing out every time we heard the door close, and we both heard it every time.
He's not the only one who's confessed this to me, either. Everyone's heard it. One of the openers even claims to feel like someone's standing over her shoulder in the morning.

I'm curious about this spirit now. No one's ever felt threatened by it, just creeped out. From now on I should take note of this stuff. Like, what time does the door closing start? I did an insanely quick Yahoo search and came up empty, although I did discover that another gas station in town sells E85. Nifty.

(And yes, I'm entirely aware that it's possible this guy was playing a prank. But with everyone noticing the same things, I have to be skeptical.)