I witnessed that flash too, it was burning before it hit the ground. So I doubt it was a control surface malfunction, weight shift, or a stall. With all the drone activity lately in the area I wonder if a drone ingestion or even gun fire from the ground could be suspect. Also what if the fuel cap was not secured and fuel was being sucked out and ignited as it was ingested? Also, there was an incident in Michigan yesterday of an explosion of a hyperbaric oxygen chamber, [Michigan boy, 5, killed in oxygen chamber explosion, officials say | Fox News] I doubt there was a chamber on board but 100% oxygen in an enclosed area is just as catastrophic.