Night of the Dead

"And so the fungi...."

You sigh, and gaze up at the clock. It's 2:00 p.m., and you can't wait 'till school ends. It's been another boring day of the same things, same classes.

Right now you're zoning out of your science teacher's lecture, something about mushrooms....?

But anyway, you're bored out of your mind, and you decide to see what's happening outside your prison window that showed a great lawn and a patch of trees blowing gently in the fair winds. A squirrel ran out and chattered to the window, although his little voice was muffled by the window, before scampering across the lawn to a nearby oak tree.

Sigh, so what now, you think this as a strange, yellow-green mist started to creep over the patch of trees, and the squirrel, several birds, and a dog out there started to screech wildly and flee....

When everything went silent. The mist continued as nothing had happened, but the animal's muffled cries had died, and everthing was still.

What the heck happened?