I'm recalling a case that happened about 20yrs ago in Minneapolis, where I lived at the time. A girl about J's age was shopping with her parents and needed to use the bathroom. The bathroom was in the basement of the store, and she went there alone while her parents continued shopping upstairs. They never saw her alive again. When she went into the basement, a worker hit her over the head with a rubber mallet (I've been scared of rubber mallets ever since) and took her to his home where he killed her. By the time the cops really started an investigation, the child was already dead, though she wasn't found for a couple of days (IRRC).
The parents weren't picture-perfect, though completely innocent. The father was not articulate in front of the cameras and was a bit odd, and people were (incorrectly) suspicious because of that.
The scenario was so bizarre because there is no way the employee had any idea that a young girl would venture into the basement on her own. But, the creep took advantage of the opportunity when it was in front of him. It happened fast. I just have a feeling, perhaps, that is what happened in this case....someone took advantage of J being out and about on her own. Perhaps someone watched her or perhaps it was simple a spur-of-the-moment opportunity.
I'm not yet willing to blame the family, though I accept that is a possibility.