If the heat is high enouigh the fire can move undergroung trhu the root system (explained a Canadian firefighter). However that was not a dead tree so don't how it can burn that way with a high content of water and no oxigen. Roots absorb aluminum dust that have been found (Canadian firefighter claim) in the soil and will make its way to the trunk. That means fuel inside the tree.
If he is on the know the rest are in the know as well. MSM is the enemy of the poeple.