No idea what it was, but it appeared to be a fireball or meteor. You can even see it's reflection in the water on the beach! It was moving pretty slowly and appeared to slow down as it was descending. Then it appeared to spin slightly or corkscrew, then I lost it among the lights of Santa Monica and the Pacific Palisades behind it and I assumed it fizzled out.
The timestamp on the photo files is 5:25pm. I just compared the clock on the camera to the current time and it was in sync to the minute, so it definitely was some time between 5:24pm and 5:26pm PST.