My character started swinging the weapon while spinning in circles.
I was in the form you get from red hearts. There was a dude sitting in the room and there was a burger in it. There were three of those little worm-like creatures, I hit 2 of them at once with a heart powered swing then the bug happened.
I never died; it was my first playthrough.
I don't remember what the room looked like. I was too fixated on the things inside of it. Sorry if that makes everything else pointless.