What is the movie "The Strangers" based on?

I know a lot of people have asked this question BUT on the synopsis it just says "The brutal events that took place in the Hoyt family's vacation home on the night of February 11, 2005 are still not entirely known" I also heard that people found the bodies of this couple all messed up and now they are just making up what happen to them. Do you think it's based on anything or is it just a ploy (a la blair witch) to get people to see this movie.