A Moon/Pluto square, psychologically speaking, removes conscious awareness of emotion. In other words, a person dissociates what they do from their feelings. Hitler had the Moon Inconjunct Pluto, and was divorced from his emotions as well.
With the moon in an air sign, a person can rationalize his feelings: they "live in the head" and combined with dissociative traits, allow for violent acts, which the person rationalizes away as did Hitler (The Jews were "bad people").
Added to the vengefulness of conjunctions to Pluto, the capacity for violence was inherent in Mr. Hernandez.
What should have at least "spoken to him" - His Jupiter (in Cancer, exalted) trine Pluto (in Scorpio) seems not to have swayed him. I myself have a Jupiter Pluto trine in Aries/Leo, fatally - an idealistic trine (fire signs). It is the strength in my soul. For those who have it, it translates as "Fairness is my God." But not in his, although he could have had jupiter squaring something. Also, a Saturn/Jupiter opposition weakens the Jupiter/Pluto trine, with Saturn/Jupiter being an aspect of an agnostic/atheist, and again, lessening the "fairness" of the Jupiter/Pluto trine, especially with Saturn being in Capricorn.
In psychological terms, he could be a sociopath or a psychopath, and those personality disorders (undiagnosable before the age of 15) are not well treated by therapists, since the person lacks a sense of remorse. Other traits in the chart reinforce this (Sun conjunct Pluto, and other Pluto conjunctions). Pluto does rule Death after all, and revenge is part of the Scorpio Motif.
Not unusual he would turn to football, a violent sport. Psychologically speaking.