A Night At The Dub

I work at a A&W to start off, when I started my supervisors told me about the building apparently being haunted by a ghost, I thought I'm the newbie and they're just messing with me. I am now a supervisor and have a key to close up and open the Dub* (short for A&W), during the summer time I was closing up with another coworker and we where a bit behind. Her ride was in the parking lot waiting so I told to go home and it was fine for me to finish up doing the last minute things like mopping and taking out the garbage.

When I was mopping the kitchen I heard something drop upstairs in our stock room where we keep things like cups and bags. I thought she was still in the building so I yelled up the stair case to ask her to bring more bags down for me, but I got to answer which got me a bit spooked but I always doubt before jumping to conclusions.

I finished my close and started to do my last walk though and turn off the lights, But then I heard VERY loud and fast steps coming down the stair case like as if someone running down them. It actually made me jump and drop my phone, I took a look around the corner up the staircase and called out to see who was up there, but no verbal answer at this point I was annoyed and stomped up the stair case thinking someone is pranking me.

When I got to the top of the stairs I tried to open the door but it was already locked, then I finally remembered I locked it already about 20 minutes before behind me with my coworker so no one should be in there at that point I felt my stomach drop and got out of there as fast I could.

Now I don't close alone and once in a while I catch a glimpes off a moving shadow in the corner of my eye in the stock room and back area, I don't know if its my imagination but still a bit creeped out by it all.