I’m convinced it was chance. There’s just no way he could have known they’d be there, or be able to intercept them the way he did if he had known.
He came prepared to hunt, and I think the girls were perfect targets.
What brought him there? Not that this guy is a serial killer, but for guys like that there’s generally a precipitating stressor; a major negative life event.
So a fight with a significant other, money issues, job troubles.
So he may have been worked up that day or something, which is why he chose that day to go out and look for a victim.
I would love to know what his devices have to say in general. That may indicate if he’s attracted to females of a certain (young) age or not.
It’s possible he would have left if he didn’t come across an appropriate target, or would have attacked any female he found suitable.