Strange bright lights filmed over Buckingham Fountain

On August 12, 2015, a family was walking near Buckingham Fountain (landmark located in the center of Grant Park, in Chicago) when a UFO made up of several white lights.

On video posted on MUFON's website, we can see an unknown object moved slowly by following a straight flight path. When they notified the object, it flew over the lake. One of the witnesses tells:

I've never seen anything like this in Chicago having lived here my entire life”.

So, what is it?

By watching video, we can think to a drone. But, a drone cannot change shape like this mysterious object.

The truth is out there...