Then you don't understand psychology. Not many people do. However it is entirely possible for someone to lose all faculty and have that lead to stupid, irrational and in this case, tragic events. So while a criminal act may take place, it may not be through consious thought.
The typical bogan approach to calling the guy a "maggot" or "animal" or any profanity only emphasises the need for much better education about mental illness.
I'm not defending anyone here or advocating the way our judical system works. I am just pointing out the very serious lack of any sort of readily accesible treatment for mental illness. Not only that, but any sort of method for identifying mental illness.
So while what happened should never have happened, it cannot be said with any sort of certainty that there was any concious awareness or ill-intent. And while unimaginably tragic, I also strongly advocate treatment and acces to care/monitoring of the mentally ill.
There is always a side that will try and use the mental illness as a defence despite not actually being mentally ill, and those sort of sociopaths can usually been seen straight through. Mental health assesment is so extremely important in cases like this one. And if there is a legitimate illness then THAT'S what the cause was, not the "person" who commited it but their illness.
Disagree with me if you like, however disagreeing in this case only means you lack kthe understanding of the issues I'm discussing as they relate to this case.