I agree: "The situation might be more complicated than SA." Don't ask me, why I'm thinking that since the beginning (though with interruptions dependent on the POI).
If the killer killed out of a perceived feeling of a threat, then I have to ask: Why did he follow the girls, why did he search for vicinity to them and even with some speed of his last steps? That would be twice sick in his mind, IMO.
Atm, I believe, he urgently needed for acting out with violence, speed, power and he expected a result, which would make him calm at the end of the attack. I think, he has done it before and for the same reason.
Why he is such a coward to chose teenagers and especially girls, I can't imagine. Hate for these specific genus I would have understood in 2017, when I had a POI, LE never had until today. There was a reason to that back then. If it is now a relative young man, who did the double murder, I can't think of exuberant hate as a reason. - MOO