There's something spooky about the building where I live

It happens often that when I enter the building late past midnight, while approaching the elevator, it opens it's doors for me before I hit the button. Not even like an automated door as it opens it while I'm at least 3 meters away...

And no, it cannot be that there's some sort of sensors that does this because it would've been consistent about it if that was the case, but this doesn't happen except after midnight....