Fortean Photography: Lights Over Lake Michigan

The above picture was taken in Milwaukee, WI, in July of 2015.  It appears to be a photograph, taken at night, which captures a lamppost and several spherical lights.  The witness describes the lights as moving "as if in unison" in the direction of nearby Lake Michigan.  Eventually, according to the witness, the lights move behind a tall building and out of sight.  So, what, then, did they see?  At first I would guess Chinese lanterns, but lanterns move linearly along the same wind currents, and do not hold a steady shape like the lights in the picture.  Nor would lights on a stationary structure explain it, as they were seen to fly behind a building and out of sight while the witness stood still.  Certainly these were no airplane lights, since they match neither the shape nor lighting pattern of a standard terrestrial craft.  I suppose it could be several drones flying in unison, but the amount of practice and coordination such a feat would require seems extreme.  But, if not any of these, then what?  Could this person have witnessed the impossible?  Are there forces at work here outside of mankind's understanding?  What do you think?  Does this mystery have an answer rooted in mundanity, or is its cause something a bit more cosmic?

Yours in Impossibility,

Tobias