Dropping the disco ball to achieve accidental kill

While playing level 5th "Hunter and Hunted" (Vixen club area) at expert difficulty, I have attempted almost over 10 times to get the timing right in order to drop the disco ball over the target "Dom Osmond" in order to achieve accidental kill rating but almost every time I have managed to drop the ball drops over his head while also causing civilian causalities.

However, whenever I go look at the place where it was dropped, I don't see any other body aside from the target's own. I am not sure if this is some bug in Windows version of the game but every time the same thing happens with no success (i.e. no clean accidental kill).

I looked around on the internet and didn't find any helpful clues except these which don't seem to work.

Press the button:

• when the target says the words "come in" or "under" while he's shouting at crowd.
• or, just after he pushes the disco girl away from stage.
• or, when the disco ball is about to align towards his position.

Any ideas from the people who have actually done this or tried over and over in order to get past it at same or higher difficulty levels maybe?