It started with momentum in an area that had recently burned and moved very quickly because of extremely low humidity and high winds.
I live near by and have ridden dirt bikes all over the area it started. It's very inexesable. They could not get to it when it was small and it took off.
Here is an amazing video that shows just how windy it was. https://m.facebook.com/story.php?story_fbid=2208918639386879...