This stuff's getting more and more sus the longer this goes on. I know that Burgerland has a really high rate of unsolved murders, but those are almost all shootouts in ghettos where no one cooperates with the cops, no matter what, while this is an environment as far from that as possible. I'm not usually into conspiracies, but I can easily imagine that the reason this happened was that Chad and his harem, or maybe just one of them, got into trouble with someone powerful enough to cut a deal with the local cops (considering that this was a campus filled with super-priviledged teens from wealthy families, I think something like that's quite possible) and said person simply decided to get rid of them for this personal reason, or they were simply disposed of to cut off someone's loose ends.