Very weird UFO spotted in California

On June 18, 2015, an automobilist was driving in an unamed city in California. By looking through window, he has spotted a mysterious UFO. This object made no sound and moved very slowly. What is it?

Witness statement:

I was driving my car through my neighborhood, on my way home when I saw it. Thought it could've been a drone at first, but object was to big and too solid to be a drone. Then, thought it could be a person in a jet pack. Looked at some pictures of jet packers in flight. There are some similarities, but nothing that looks like what I saw. It moved very slowly from right to left as I was viewing it towards the east. I watched it for about 15 minutes. I have provided the original pictures with their respective zoomed in versions.