Black cube-shaped object captured in the clouds over Texas

A motorist driving on a highway in Texas noticed an object in the sky on which he started to film the strange anomaly. 

It is not the first time such a cube-shaped object appears in the sky over Texas, though the question is whether the phenomenon was a UFO or just a tall building, a mirage or a reflection in the window. 

Anyway, take a look and decide for yourself what the object could have been.