Anyone else see this?

Saw this in 2014.
What I mainly remember, is being more terrified than any other point in my life. Mostly, I think it was the thought "OMG, they're real. They exist" is what terrified me most.
The square protrusion is what stood out as being the most distinctive feature.
It wasn't moving in ant sort of rush, nor was it much higher than 100 to 200 feet from the ground.
Has anyone else ever seen this design?