My experience as a former security guard

I was a security guard for a prominent radiopharmaceutical company in the Northeast. We had to wear dosimeter badges and record temperatures of materials in hot (radioactive) areas for our daily logs, but there were also many different buildings at this site that we had to perform perimeter checks and on-foot tours in. One of these buildings was a facilities and engineering office that was located next to a former R&D building that was later demolished after a report came out that revealed they were using animals to test their products. 

One evening I was doing a tour of the facilities and engineering building. Keep in mind the layout of this building is very unsettling, since it’s basically an old two story building with one elongated hallway on each floor with offices and rooms left and right. Regardless I completed my check of the first floor with no issues but as soon as I walked upstairs to the second floor I heard a loud scream coming from down the hallway. Nobody was in the building except for me, and there was no way that any animal or even a human could produce a sound like that. I panicked, and quickly checked every room but could not find any trace of anything. 

On another shift I tour this building again and as soon as I reach the second floor I see something move from one corner of the end of the hallway to the other. A little blur was all I could see. Now my hands are sweating and I’m trembling with fear, and I decide to just get the fuck out of there and return to the guard shack. 

That night I go to sleep and have a dream that I am at work doing a tour of the same area on the second floor but in this I have a more horrifying view of what I saw. This dog like creature with wings was looking right at me with no emotion whatsoever. As I type this I am getting chills by how surreal this experience was, and needless to say I thankfully didn’t last much longer at that site hahaha.