Weird noise, not sure what it was....

At my old work, where I worked as a cleaner. I wasn't allowed to record and I can't give an exact location but its based in Australia, Melbourne, Victoria and a government site. This happened back in 13th Dec 2019 I believe, from the video's date. It was roughly anywhere from 6am to 6:30am, no one else in the building at that time otherwise I would of heard the big door close/slam as someone walks in.

This was the 2nd time, I had finished cleaning the kitchen when I first heard the sound. As a joke as I didn't think anything would come out of it I said "who's there and it stopped" but a little different to the one I recorded. It slowed down before coming to a complete stop. I was a little stunned but I only had 5 hrs to clean a bunch of bathrooms and kitchens so I went and did the female toilets (I may of done the males and then the females, I mixed it up but don't remember the exact order on this day). But I have just left from the females bathroom when the noise is starting again.

That's when I started recording (On my Samsung Galaxy S6 at the time) I walked into the room where the sound was coming from (I didn't the first time as i wasn't near it and was coming out from the kitchen). At first I thought it was how odd it happened twice, stopped soon as I asked who was there. Playing it over and over just recently on the TV, right after I ask "Who's there" you can hear some footsteps, walking away. The building is old and has been around sine the 1856-1872 and when im walking you can hear the floor creaking and such but when you hear the footsteps, im standing still and the camera isn't moving to show I was moving (something im not great at for holding phones steady).

Some questions people may ask/wonder

What was making the noise? I'm not sure, I was thinking it was the heater that's located up on top of the roof. It only happened this one time but I was freaked out for a few weeks or so ever since this happened. 

Why didn't you turn the light on? I'm a cleaner who is to do bathroom and kitchens, I had no business being inside that room and I'm not sure if they would believe me if I said "I heard a noise and checked to see what it was" even though there was no top secret things that i could have access too (as far as I know) they were very big on security.

If you can't record or take photos on site, then why are you uploading this? I no longer work there, I don't list where I worked and I doubt this video will get any big attention lol.... So taking a risk to some degree, but eh. 

So yeah, think whatever you want to think everyone has their opinions and stuff just thought I'd share.