Somebody had commented something in regard to the killer maybe having a personaility disorder and it being the reason they could resume behaving "normal" the days and weeks after the murders and it got me thinking and revisiting information on Personality Disorders. Here are some of my thoughts and links on that.
I feel three "Personality Disorder" types could fit this type of crime, meaning, in which the way it was committed and to who the victims were. I have no official education of these disorders, just personal observation and referencing materials. But...
My guess would be of the three, two would likely be detected through behaviors noted by witnesses after the crime and/or during interrogation. Those disorders would include Paranoid Personality Disorder by itself and Obsessive Personality Disorder by itself. The one I would guess would have possible success in pulling it off would be number 3. Antisocial Disorder. Antisocial with Paranoid and/or Obsessive undertones would be the perfect cocktail.
This is just one example of what I used to bounce my ideas of:
http://www.mayoclinic.org/diseases-conditions/personality-disorders/basics/symptoms/con-20030111
Like I have said, I am not a doctor of any kind, nor do I have delusions to think I possess their knowledge. I am however a bit of a paranoid personality type in the fact that I'm always analyzing people, their actions, their words, how they word things, facial expressions, body language, possible motives, and so on. I am always trying to figure people out or at least making mental notes. Maybe this is why I'm attracted to missing persons cases and unsolved murders.
With that being said I feel this was a mission and it had to be lead by a sort of person that was controlled and/or disciplined and he was prepared and planned emotionally and mentally.
Not high, not spontainious, not emotionally attached to the victims, and I would not use the word rage. Rage by definition includes loss of control. Which would lead to a more spontaneous killing or getting caught up in the emotions and drifting from the plan. I feel the word rage would suggest a more animalistic type slaughter, would be more messy not exicution style killing. Stabbing, beating, torturing, more victimizing than just execution. Maybe fixation, disdain, contempt, hate would be better words to describe the emotional state, for the leader of this anyway. If one or more persons in this group had harboured a more rageful disposition or feeling towards the victims they would be seen as a liability by the leader. They would have to be controlled by the leader. That person being quite unstable would likely leave behind more evidence and more likely to come unravelled afterwards. More likely to snap under the pressure of interrogation as well. I believe IF the leader of this killing was so organized he would choose his partners wisely.
http://healthresearchfunding.org/antisocial-personality-disorder-statistics/
*As much as 80 percent of male prison inmates were shown to exhibit signs and symptoms of antisocial personality disorder.
*The prevalence of antisocial personality disorder is higher in treatment programs where patients are abusers of drugs or alcohol.
Note: Take into consideration that being an abuser and being an addict are not the same. Many people in attendance of a drug or alcohol programs are court ordered and are not seeking help.
Once again, JMO. Most everything I post is just my opinion and nothing more, other than the links I share.