Short Horror Film Script

I am by no means a professional Hollywood screenwriter. In fact, the script I'm working on right now is my first screenplay ever. I'm more of a short story writer. The problem with a short, obviously, is there just isn't very much time to develop characters. Our aim with our movie is 30 minutes. Now, without just getting right down to the action, we have only a few minutes with which to introduce characters, give a back story, get the action, climax, and end the film. I'm not going to give away what the script is about specifically, but I will say its a slasher type movie taking place during a camping trip. I'd love to hear from others who have written amateur horror movies and specifically shorts to see how the character development problem is addressed. Also, anyone else with ideas of how to develop characters quickly. Shorts, to me, are a "bite sized" movie, yet I do want a complete movie, not just another hack and slash waste. I’m using a character to narrate the history of the villain through a campfire tale, which I think is the most logical vehicle, but again, 30 minutes cuts down on the amount of time I can show setting up camp and all that jazz. So, any cool and unique ideas?