It most likely is a harassment, as it is directed at the photographer; a warning telling him to stop taking pictures. There was a series of photos sometime ago showing a Z-9 doing the same thing.
From the quality of the video and the fact that there was video, I'd say chances are it was taken with a smartphone instead of a dedicated specialist camera with a massive zoom lense.
That would make it pretty hard to spot that someone was filming them from the Z10.
Also, if you are concerned that someone might photograph/video your attack helo, don't go flying it over a densely populated urban area, and if you do, don't be surprised that people will whip their cameras and phones out to take shots.
In addition, it seems a very counter productive move to be hovering and literally flying circles around someone if you were upset that they were taking photos. if you don't want them taking photos, you fly away as soon and as fast as you can.
Seems to me more likely that the pilot was showing off if anything.
Maybe he saw a pretty girl waving at him from the playground and thought what the hell. From the surroundings and the size of open area, I would also say that it was a university campus instead of some school playground.
Also, judging from the reaction, or rather lack of one, from the kids playing basketball throughout, it would appear that this display was nothing too special for them.
