While building a rather nice new place for my villagers to stay I noticed something quite unfortunate.

It appears as though villagers will quite happily use fireworks in enclosed spaces to celebrate the end of a raid. Which was quite nice... until it caused mass death, mayhem and carnage as their own fireworks killed them. Needless to say the entire village was wiped out and will have to be repopulated.

I can't imagine that it's intended for this to happen, so I'm reporting it as a bug.