Now while most facilities don't have fire extinguishers capable of putting out metal fires (when metals burn they produce their own Oxygen which means you can't snuff it out or douse it.). However, I do find it damn convenient that the camera just happened to snap a photo right as something exploded inside the notebook. Yes, there is Magnesium in a D505, but it takes a REALLY hot flame to ignite it. Remember high school chemistry class? You had to ignite the Mg with the blue flame of a bunsen burner. Most batteries don't burn themselves, but they get hot enough to set something else on fire.
All in all, this is an isolated incident at best. There have been more Apple notebooks catch fire from their battery than this.