What the hell is going on with the quotes on this page?!?!
Anyways, OP, I'd talk to the man after you get your head wrapped around what was lost. He called YOU to tell you and probably work towards a solution. Might be a bit early to figure that out, but the line of communication is open and he knows he caused a mess. That's 90% of it right there I think. His insurance should cover your loss, since it was his fire started on his property. Fire/Police and all that are already involved, I would see if they reach out to you as well.
Funny to me that he had to call you, I know you said your kids live there, but didn't they notice their land burning down? Not my business though.