I was trying to film the local fireworks from above my house (which is in the country and less than 4 miles from the fireworks) and, what appeared to be a low flying plane or ultralight flew in from a few miles away, and flew right at my Phantom. It later did a 2nd pass right over top of me. I was only at around 300 ft, and lowered quickly because it looked dangerously close. It looked like another drone at first but it was loud and sounded like a gas motor. The "ufo" lol, flew in what looked like a large circle around the fireworks and over the city, going out of its way to check my P3 out. I didn't think low flying aircraft like that were allowed to fly that low over city limits, does anyone else have any knowledge on this? What it most likely was?