I have also seen heroin
While I haven't seen anything in the very limited evidence to point that way, I wonder about heroin, along with meth and shatter. Not because of anything specific here, but simply because those are the current issues being faced across the county. Killing 8 people tends to point in the direction of something large in terms of motive. The reported number of MJ plants is smallish, although there could be more, those could be just the clones (or source for clones?).
I also think that the numbers killed points away from relational killing (personal beefs over cash, land, spouses or exes, etc). Getting even doesn't require an entire family--even if one is worried about potential witnesses. Ditto theft.
So--while I think that the terminology "Mexican cartel" is both vague and inflammatory, there is evidence of organized crime connections with Mexican nationals within the county. Likewise, there is plentiful evidence of gang involvement in drug distribution in the closest markets: Detroit, Chicago, Cleveland, Columbus. I believe that there was also a note that among the first horde of folks interviewed (30-some?), many were from Chillicothe--which has been sorely drug-plagued simply because if its location on 23 (probably also unemployment).
Agree that IJ was most likely a wannabe. On the other hand, when he and friends showed up in the immediate area, it seems they punched some buttons. Maybe the Rs were expecting someone else?
Anyway--if I were LE, I would at least be looking for a reason to rule out some things like heroin, meth and shatter.