Alien Zombie Apocalypse

Here's a wacky dream for you.

I dream The Husband, boys, and I are out for a Sunday drive when circles appear in the sky.  These circles carry the message that alien zombies have been living on earth and are now taking over.  Everyone who is an alien zombie is now law enforcement.  Everyone who is not an alien zombie must gather in a giant arena for "sorting".

Our family decides not to gather at the arena.  Which is good, because their idea of "sorting" is what we consider mass slaughter, actually.  Instead, we go to our house to collect supplies for survival.  While we are home, alien zombie security guards show up.  Although scary and heavily armed, they are not too bright.  They think because we are still alive and not dead at the arena, we must also be alien zombies.  In fact, they are delighted because they've known us for so long and had no idea we were one of them.
We play along.  Invite them in.  Serve them beer.
The Husband then suggests something which sparks a fight among the alien zombie guards.  Their discussion gets heated, and they shoot each other dead.

End dream.
Discuss.