This was a window of opportunity if that's what the perp was waiting for, she usually walked with her friend to school, it was snowing a little and more kids were probably being driven. I think maybe he planned that as his opportunity, if he was waiting for one, so he would know the news, like where he put the backpack, street name, a child had been killed around there. He would also know the history of where he put her, to add the creep factor, it was known for being haunted, maybe even knew maintenance would go there and find her.
He's old enough to get away with this so far, so I keep thinking someone in their 20's, early 30's. He probably likes horror movies, crime shows like CSI, Criminal Minds, maybe, but he could also be a gamer, loner, into the computer *advertiser censored* chatrooms. You know they're searching that angle, anyone into sadistic child *advertiser censored* and has stood out in these chatrooms. If this is his first crime, he's sure been fantasizing it long enough, because he's been good, so far, at not getting caught. JMO and I could be way overthinking this case.
. If the vans have no windows, they move up the list.