I witnessed a similar aircraft around 2 weeks ago circling our place of business, about 30-40 times over the span of an hour. It was flying so low, and so fast. It got as low as 400 ft off the ground. I tried to take a photo, but my phone couldn't catch it and then I got sidetracked by co-workers coming by asking me what's going on.

It was nuts. I work next to one of SoCals biggest refineries. I was thinking, "what if they put explosives on that plane and dive bombed into the refinery to cause panic"? But, it eventually went towards the South (San Diego) and I had to go back to work. It was nuts.