Plumbing issue...urgent!

this morning approximately 2am, we got woken up by the loud noise from upstairs. went up to complain about the noise, the guy answered the door said their pipe is clog and they r working on their pipe.
came back from upstairs,only to find our kitchen sink is overflowed with some black,oily smelling fluid.
went up again right after, nobody answered the door, again this morning at 11:00am, nobody answered the door either.
called capital centre emergency contact number already and they said someone will contact us.

not an expert in plumbing issue, seek for some speculations/opinions of what has happened.
could this be caused by the guy upstairs tried to flush the clog down and only further clogged the main pipe?
we have already cleaned out most of the overflow out of the sink, but could there be more coming as ppl start using their kitchen sink?
any suggestion on what we should do next?
what a way to wake up on a saturday morning

unlucky

Yeah, that is quite the unfortunate Saturday morning. The entire building has been experiencing sewer and drain back-ups recently. Over the years, people simply don’t use common sense when disposing of certain things down the drain (coffee grounds, oil/grease, renovation debris and byproduct) just assuming that when it’s down the sink, it’s gone!

Well it’s certainly not. It sticks around and causes quite a few issues, just like the one you're describing.
Fortunately, the board has taken note of this and we are currently in talks with certain specialty cleaning companies to arrange a thorough cleaning of all the pipes (hopefully sooner rather than later).

In the meantime, some people will experience issues like this. If you are a renter (from the rental pool), I'm sure the rental pool has a phone number in place that can be dialed and someone can address the problem. If you are an owner (or rent directly from an owner) then the issue would best be solved by you(or the owner) addressing it directly, and then afterwards compensation can be sought and awarded if deemed appropriate, once all the details of what happened come to light.

Pipes

Harry came in on his day off (yesterday; he also wasn't the staff person on call) to help the plumber deal with this situation. I ended up walking around with them both for some time. Hopefully, everything was resolved without much further issue. For everyone.

This is as issue that I have on a regular and ongoing basis, as I live in a unit on the bottom of a stack. So, until people learn that dumping anything other than water into the drainage system is going to cause a problem, the steps the Board takes to flush out the system won't much matter. The same problem will continue to occur once new build up starts plugging up the system again.

However, that isn't to say flushing the system won't be valuable, if only so that the current rash of overflows are eliminated. In the meantime, I suggest doing what I have to do. Keep your drain cap in your sink at all times, which will prevent the drainage system from regurgitating its contents into your sink, or worse, onto your kitchen floor.