I don't have any ideas for the "killer sheep" yet, but the "Moon on the Hill" thing is inspiring all sorts of images...

...then again, how about this?

Your bitter heart
Will make you weep
One day you'll pay
For abusin' sheep.
'Cause we have your gun
And we can use it, too
Your bitter heart
Will have a hole right through.

cho:
When police come
And find your ass
We'll just act dumb
And chew the grass
You'll be dead
And they'll be had
They won't suspect us,
Sheep gone baaaaaad.

Your bitter heart
Will stop someday
We'll be on the lamb,
But that's ok
There's mutton now
That you can do
Your bitter heart
Will have a hole right through.