Four in forty?

What kind of serial killer kills once every ten or so years? That sole aspect of the plot made no sense.

The only link in the killings was no blood. And any locals believing there was a vampire in the woods would know feeding once every ten years in not how things typically are. There would be a lot more dead or missing people.

Not sure why any of this was supposed to make sense... even on a horror movie logic level. For a horror movie to be truly effective it needs a foothold in a reality that can be related to.