Late night working

It was around 12 am, there's knocking sound coming from upper level of Block B ( level 19th) which can be heard very clearly.

Apparently, the occupant was doing the work for the past minutes. I confronted the owner cause failed to get the security guard. The work stop for a while but was resumed after few minutes. I managed to get the guard later on. It was at 1 am. The knocking sound completely off.

It seems that there's piping problem. But can't they do it the next morning. Please think about others!