I transferred from the Banning substation to a warehouse in Ontario, California. I had a rotating schedule, two nights a week I worked graveyard. I made good friends with my normal graveyard guy, and after a month or two we started noticing odd things. It started out with cold spots in certain areas of the docking yard. I noticed the first one on the west side of the docking yard. I started noticing odd flashes of light when the warehouse was closed, shadows inside the building moving too fast to be human, the porta potty door opening and closing on its own, odd reflections in the mirrors of my truck, etc.
My graveyard guy showed up one night to relieve me from duty and we started talking. Out of the blue, he starts asking me if I've seen anything weird. He described everything I had seen to that point. As we were discussing it, I started noticing the weird lights and cold spots. After about fifteen minutes, nothing else seemed to be going on. I went home, and came back the next afternoon.
I was sitting at the desk inside the warehouse at about 2030 (PST) when the last supervisor comes up to my desk and asks "was that you?" I was completely confused by his question, so I asked what he meant. He explained that all of his crew was gone (I verified via sign in sheet) and he heard a knock three times from one of the support beams. He said it was far too loud to have been the beam doing it on its own. He went on to explain that there were desks and such around his work area, so he thought maybe I was trying to pull a prank on him. As he was explaining, I noticed a shadow move at the back of the warehouse. I got up and started running to where the shadow had been, and I yelled back to have him check the security camera feeds. I couldn't find anything, and he didn't see anyone in the warehouse, but in playback saw the shadow. Sadly, the chief of security for that company is VERY uptight and won't let us copy that footage.
After we locked up (by now about 2130 local time), I went into the docking yard where my graveyard guy was waiting for me. The supervisor left, and we locked the gate. All the lights had been off inside and suddenly came on. There was a motion sensor to activate the lights, but it would trip the ADT alarm as well. No alarm went off, but the lights came on. We started seeing shadows and lights passing by the docking door windows erratically. We went to the window and looked in to see nothing out of the ordinary.
I decided to leave at about 2300, to get a call from my graveyard guy calling me five minutes later telling me the power went out. Almost every night this was a normal event.