Every loving parent wants to know that the pupil of there eye is protected, excepted, and respected under any situation; especial in a place where they spend most of there time in. How are they cretin what these expectations are being met then a parent does not see it with there own two eyes? Most parents are clueless about what happens to, and around there children when they are away. This does not mean adult are failing as parents but,  they are however failing communication with the kids. A child in a unpleasant situation with not open up to anyone without fear of being judged, harassed, or punished by there guardians.
What is a confused and scared  child to do in situations they feel they have no control over?  To them no one can  help so they keep there situations and emotions bottled up for no one to see. The stress of the unfix able problem is like dry ice on a sealed tight container, eventually they will blow. That blow can end is a physical release as in killing the problem that has bothered you for so long.
It take one problem to evolve a person into a totally unrecognizable creature, this is how I believe serial killers are created.
A person can only take so much  pain and abuse before it turns into pure anger. Then an urge to make those to made you suffer, suffer the exact same pain the victim has been suffering. There hurting body is not enough to satisfy the urge and then progresses, it starts with one victim then the next and so on. It turns into a disturbing hobby and the killers learn to live with this on going urge. They learn to live normal  unsuspicious lives, make a normal family even.
That is how Alice and Gerald Uden  raised there daughter, with shocking secret that she has recently learned about. The Uden's daughter no longer sees the loving parents she once knew, now all she sees are strange killers. Although her parents dark secret is disturbing. Her parents are not to blame for being killers, there scaring childhood or physiological problem are to blame not her parents alone. They did not choose to be the way they are, they where molded into killer.

http://www.news.com.au/lifestyle/relationships/erica-hayes-shocked-over-parents-murder-charges/story-fnet0he2-1226808310704