There was a burst pipe. This was making three weird sounds happen:
1) The water rushing out of the pipe was making a ringing sound (like if someone is taking a shower in another part of the house)
2) All the water dripping from the ceiling was making a lot of drippy sounds which sounded extra strange because of the crazy acoustics on this floor.
3) At the end you can hear some electrical buzzing where the water was pooling on top of an old light fixture. I stopped filming and tried to fix it but just wound up blowing a fuse and nearly burned the place down in the process. The security guard was pretty understanding