If they continue to do it, I would think it is because they have been successful at some point. Which brings up this question.. What are the percentages of these people actually having sex with these kids? Pretty sick to think a lot are getting through at some point without getting caught.
If they show up to the house they should be shot.
I like your thinking, but shotting them would be to easy of a way out. Put them in jail, in the general population and let them fend for themselfs.