When landing a helicopter, I guess there are a few basic rules to follow. Make sure you don't land on people likely comes first, but a close second is probably to avoid landing near things that stand a good chance of getting blown away. This pilot didn't remember that part.
It's Polish Independence Day, and like in any other country, the youngins love celebrating their country's liberty by destroying parts of it. "Youths" butted heads with (and threw things at) riot cops in Warsaw. Check out the view from above.