UFO Spotted Over Pasadena, California, Aug. 16

My brother was on a walk and caught this unidentified object on video with his iPhone. He apologized for not keeping the object on screen the whole time. He was watching the object with his eyes at the same time because the object of course looked a lot larger in person than how it appears on camera. He spotted it around 7:00 pm above the Pasadena, Old Town area. The object was rotating silently at what appeared to be around 500 ft. It then climbed to about 2000ft and gained speed gradually as it flew away. The video shows the object's extremely reflective surfaces. Comparing it to the Light aircraft that flies under it, in video part 2, it looks to be around 50 to 60 ft in size. Please leave comments if you might have an idea of what this object could be (weather balloon related, aliens? etc.) Watch the video in full screen mode for a closer look.