If memory serves, one of the huge fires in Arizona a few years back was set by a firefighter/arsonist. If you're looking for a fellow who knows what he's doing ... a firefighter is a good first guess.
Apparently it's not all that uncommon for pyros to become firefighters.
Earlier Wednesday, the California Highway Patrol arrested a motorcyclist who was caught setting a brush fire in San Bernadino County, near Lake Arrowhead. It is not known if the suspect, John Hund, 48, of Hesperia, was responsible for the fires that ignited Sunday in that area.