Are small-town cops really so incompetent they can't catch these idiots?

Looking at all three AU movies, the really incredible thing is that these mouth-breathers with IQs that barely break room temperature can kidnap and/or murder at least 20 people, many in broad daylight, most in the same geographical area (where they also live), leaving prints/DNA everywhere (and also almost certainly being recorded on security cameras at least once--like the convenience store)...

...and never even have a cop knock on their door to ask a few questions. I mean, I know they live in some crap exurb in Pennsylvania or whatever, but are the cops really that indifferent/incompetent?

And it's not like they only killed prostitutes/druggies and other "forgotten" members of society who don't have much in the way of family and friends who would go crazy trying to find out what happened to their loved ones. They killed quite a few respectable people and families too.

For example, think of the crime scene at the end of "Mordum." We're supposed to believe the Keystone Kops just looked over the blood and poop-covered slaughterhouse scene and said "Whelp, this sucks. Doubt it's connected at all to that security camera footage we had from that convenience store assault a few weeks ago. Let's get some donuts."