Alternate ending
I got the R2 DVD release from Amazon.de. The deleted scenes include an alternate ending. When the cop shoots Elizabeth, he hits her in her torso, not her arm. It's clear she's mortally wounded. Bobbi runs out of the room, as Sam supports Elizabeth. He says, "Hold on, babe, I'm coming," and shoots himself in the head. Bobbi runs outside and finds Stephanie holding her Blackberry (or video game or whatever that is) and looking into the distance. She says, "I saw something bad." The two survivors walk away together.
At first I said, "Naaah." Then I decided I kinda liked this ending after all.
Next time you see me, it won't be me