I don’t think it’s random.
They knew or encountered the killer on some level, even if it was just before the crime. Could have been they were trying to score some drugs but had no idea how and reached out to the wrong person.
Could be one of the girls rebuffed some psycho, and he got pissed this dude was hanging with 3 girls including the target.
Personally, I think it was even less incidental then that. It wasn’t some serial killer passing through town. At least one of them knew the killer before the crime happened.
That had occurred to me as well...........................
Maybe it was payback for white eyes stealing the land?