why?
what illness?
the zetas in mexico have killed thousands in all sorts fonfucked up ways they arent mentally ill.
sane people tend to be the biggest killers because they do it with a goal and a reason
Well mental illness is a pretty broad term and is constantly expanding. It is essentially ways of describing a lack of normal behaviour (either through biology, chemistry or psychology) . Simply the suicide could be classed as a mental illness technically.
Definition of mental illness
:any of a broad range of medical conditions (such as major depression, schizophrenia, obsessive compulsive disorder, or panic disorder) that are marked primarily by sufficient disorganization of personality, mind, or emotions to impair normal psychological functioning and cause marked distress or disability and that are typically associated with a disruption in normal thinking, feeling, mood, behavior, interpersonal interactions, or daily functioning
Mass murdering defenceless civilians would not be associated with someone who was displaying normal behaviour, interpersonal interactions, or daily functioning would it?
It is a massive can of worms admittedly but I have no doubt that a medical professional would have not deemed this mans behaviour normal.