None of that explains the subject heading (which comes from the title of the article, no fault to Morgana) and says: 'senseless but justified'.
Here's what the article - regardless the title - actually says:
Kleine said the death of Scurlock was "senseless," because the situation stemmed from what was meant to be peaceful protests. Kleine said the determination has been made that the shooting was in self-defense. He said that there is video evidence that he wants the public to see and that the decision that has been made is based on all of the information the office has currently.
Let’s reiterate the “justified” angle.
Scurlock, the violent looter, was 0% justified in attempting to attack Gardner, the victim.
Gardner, the victim, was 100% justified in shooting Scurlock, the violent looter.
Easy peasy. Nice and easy.