Using common sense though, in this case it seems the probability would suggest that a young teen used an extremely potent painkiller, 40 times more powerful than heroin, incorrectly, and paid the price. I doubt marijuana played a significant part (perhaps any part) in this at all. If you notice, one can realize the greater probability he died from fentanyl because 1) the other boy using fentanyl along with him is in bad condition with permanent liver and muscle damage, 2) it occured on the same night, and 3) things like this have been reported from fentanyl abuse before.

It seems you're just trying to pick it apart when it's fairly probable based on the known evidence that the conclusion drawn, the boy overdosed on fentanyl, is correct on the known facts.