Heard what sounded similar to a turbo diesel engine but we knew that it wasn't that. We all began to investigate the sound,

My neighbors and their daughter was sitting on our porch talking. Ironically, I always like to ask people if they believe in UFO's which i did and of course that started our neighborly debate. Roughly 1-3 minutes later we heard what was similar to a turbo'ed diesel engine. His wife looked at me and said what is that? Her husband turned and looked up the street waiting for a vehicle to speed down the hill. Their daughter went out on the sidewalk and said, well Bob, it looks like you might be right about UFO's. At that point we all ran down onto the sidewalk and saw a square object fly about 100'-150' over our house.
The square object had lights in each corner of the square, with 3 of the lights being white, one being red. The square object seemed to fly with one of the corners being in the front. It did not fly with the flat side. My wife looked at her airplane app that tells what planes are in the sky and there wasn't any planes showing. The thing that bugs me the most is, four adults saw this, all of which had cell phones in their hand or pocket and we all just frozen and watch this object fly by.
NOTES: As I thought about this all day, the only logical explanation I can think of is that the turbo engine sound we heard was a gas power drone taking off because we heard it and as the object flew over us, it was silent. However, this object was much larger than any civilian drone.