I think it's a bit abrupt, yes. The way you have it set up, you're showing instead of telling. And so much about their trip is skipped, it has me wondering what happened while they were there, and how the fact that they were camping is even really significant.
It definitely has a spooky feel to it, which I'm sure you were going for. I would just either expand on the beginning--write about their trip, why they're there, etc., or leave it out all together and start with the person being afraid.
(heh...I just got flashbacks of "The Blair Witch Project")
