Jones, 37, was a single father and computer engineer who, after killing one of his children, decided to kill the other four rather than allow them to end up with with his ex-wife, prosecutors said. His lawyers are expected to argue that his mental problems were worsened by drug use and his wife's infidelity. Source 8f.
His lawyers can try to bring up mental issues and problems but at the same time I think it goes a lot deeper than that - there's obviously a powerful hate or greed that seeps into this person that if he's not satisfied with whatever result, he will take matters into his own hands in the most gruesome way!
International Level: Envoy / Political Participation: 240 24%