Squirrels in the Ceiling

I just discovered lastfm and I can't even listen to it.
There are squirrels in my ceiling.
And they are playing tag.
And hissing.
I didn't even know squirrels could hiss.
Their little feet don't even pitter patter like you would think.
No.
They thump thump thump.
Like giant radioactive squirrels.
Even if I hit the ceiling with the blunt end of our shopvac, they continue to scurry and thump.
I'm not sure how they're getting into our ceiling, but every once in a while I see them hop from the vicinity of our roof to the trees nearby.
Oh god.
I think they're killing each other.
I have this image of squirrels in battle armor jousting with branches above my head.
Battle cries and all.
Or maybe they're just mating.