[Hareoic]

Well, if you need a crazy theory, how about tiny grappling hooks that were shot into their stomachs and then yanked out, pulling their organs out with them.

Or a slightly less crazy version would involve fishing hooks.

Also, perhaps there was something in the food after all. Something metallic and magnetic that tore right through them after being drawn to an electromagnet activated beneath the table (or cleverly disguised as a decoration at the time). The culprit probably shut it off and removed it after that (otherwise the gold bar is fake or heavier than we'd guessed) and filled them with candy for some inexplicable reason. (I'm pretty sure it was mentioned the candies were still wrapped, so they probably didn't eat them before dying/being torn open).