Dark Gray Mass Over Southern California

Out for a walk, heading east. I am a bit of a skywatcher and a couple of lights had caught my attention. On the second light, a dark fuzzy object popped out from the darkness. It was about 60 degrees up and I estimate about 1 1/2 miles away. It had no lights. Gray and hazy with no discernable edges. An out-of-focus Brillo pad wrapped in yarn would be one way to describe it. About the size of a 3 bedroom house and traveling around 300 mph. It flew from west to the east in a straight line with some up and down variation. My sighting was brief, but I got a real good look before it scooted off into the night.