I am far from an expert, but one possible scenario revolves around drug novices who are partying heavily, and a simple problem communicating. A group of tourist

I am far from an expert, but one possible scenario revolves around drug novices who are partying heavily, and a simple problem communicating. A group of tourists, well into a night of very heavy partying, could ask a random person for an ambiguous term (like 'powder') expecting to get cocaine. Perhaps that particular dealer only has heroin, which is technically a powder as well, so he/she sells it and thinks nothing of the transaction. Moments later, some very intoxicated tourists dive into what they think is cocaine. They do a line each, don't get the cocaine feeling that perhaps one or two of them vaguely remember, but they assume that they just got badly cut drugs, so they dive in and do more. Snorting heroin (especially if you think it is cocaine) is a surefire recipe to die because it tends to take a little longer to really kick in. And, because of its toxicity, there isn't a lot of room between getting high and dying.