http://www.businessinsider.com/most-mass-murderers-arent-mentally-ill-2012-12
Thanks for the link Scipio.
The article actually states "Mass murderers are not, according to statistics, mentally ill in the psychiatric sense. That is to say they are not living outside reality".
It then goes on to say:
"The most common characteristics are social isolation, introversion, withdrawal and a relative deficit in social skills and relationships. At the same time, signs of paranoia can also be observed. These people often believe that people are after them, bullying them or ignoring them".
"These features of course do not make someone a murderer. For a person to commit an act as extreme as mass murder, these characteristics have to be very intense. On top of the paranoid behaviour, there is also megalomania and self-centeredness".
The above doesn't sound 'normal' to me Scipio?
Random one-off incidents of murder are usually brought about by crimes of passion, anger, substance abuse, where a person feels under threat etc. Over and above this eg the case of Adam Lanza and WHF as far as I can see there is always some underlying mental illness and/or personality disorder.