Wow, that's got to be seriously investigated. As I recall, that courthouse is part of a much larger, almost brand new complex. I'm assuming that the contractors followed fire safety regs - which should have prevented something this big...
A google news search reveals that their fire dept has management problems (on third chief in 3 weeks). (wash post article, afraid to post it).
We did occasionally get an arson, but those are mostly insurance fraud.
I do recall one case (not mine) where a couple of felons burned down the Fayette County GA courthouse on the mistaken impression that if there wasn't a courthouse they couldn't be tried . . . that was a pity because it was the oldest courthouse in GA, with a hand-hewn pine main beam some 85 feet long. They did save the beam and made it into a bench . . .
We'll just have to wait for the word, I guess. But given that it was under construction, that's where the smart money will bet pending the arrival of the fire investigator . . .