No discipline... the route of most of society's problems... sorry to hear that...
How hard is it to stop an accidental growth of your camp fire? Unless he was 'stoned'/ out cold /left the fire without putting all cinders out..? If he made the fire against the wood wall then that would be arson I imagine.
Still.. I guess you can't dwell on what's happened too long as it can't be undone now. An awful shame though. Sorry