Your theory sounds very plausible, up until I got confused over your last sentence I bolded. I am not clear on what do you mean, she was definitely targeted? Do you mean Somer in particular, or any child that could have been walking alone that particular day?
Both. I think any kid would do but this was someone who knew her and most likely someone who disliked her. The opportunity was there and the motive was his rage. I know Somer wouldn't go with a stranger. So it was definitely someone she knew. Prime suspect SP, second PC and third neighbor or someone from school. The fact that she died the day she had a fight with someone at school is very strange to me. Someone was mad at her. Maybe there was feud going on. SP could have been asked to help and ended up killing her. It could have been a teen in the neighborhood Somer often spoke to. Kyle is kind of suspicious to me as well. The guys that did work on Gano too. I wish this would be solved already. This killer needs to be punished.