Sexual preditors of all types usually stick to certain patterns of behavior when determining who their victims will be. They also are ritualistic in how they victimize them. Remember BTK who was fairly recently caught after several decades of committing sexual crimes? He kept to certain patterns of behaviors of which he described to the court when he allocuted his crimes. His descriptions would be considered textbook examples of how the mind of this type of perpetrator works. This guy in Missouri is probably not much different in that he sticks to his own patterns of determining victims ages and looks etc.
In terms of "punishment"? IMHO, a bullet to the back of the brain works for me. The damage these perps do is enormous and far reaching. Often their victims become victimizers themselves. There's little hope in ever rehabilitating them, and the vast majority will always reoffend if placed back in society.
Preventions? How do you prevent someone from developing their desire to commit such horrid criminal acts against children when we don't really know why they develop these desires in the first place. Not every person who was molested as a child becomes a child molester. So, that is not the only cause of their behavior. We have to have a better understanding of the brain and what areas are involved when dealing with someone who "craves" having this type of "relationship" with a child. Other than locking them up for the rest of their lives when they are caught, or just killing them outright, I don't have the answer (or I would be writing books and making obscene amounts of money). Abnormal human behavior is as old as humankind.
I think so much hinges on the innate personality of each of us.
...how the mind of this type of perpetrator works., along with ...a bullet to the back of the brain and There's little hope in ever rehabilitating them...
I'm understanding that you look at it as a mental aberration, not a deliberate, evil choice.
If so, I also agree that we simply cannot give "sick" people ("crazy" is now politically incorrect, I suppose), the freedom to do evil things.
The woman who drowned her four children comes to mind.
How to determine who deserves punishment and who does not.
And somehow most of us stay sane despite all the grief. Amazing!