Heroin disguised as SweetTarts found in Upstate NY

[pdq]

It's not even the worst morphine analog. Sufentanil is ~5 to 10x more potent by weight than fentanyl (which is in turn 100x more potent that morphine). But carfentanil is about 20x more potent than sufentanil. The LD50 for fentanyl in monkeys is ~0.03mg/kg. No one knows what the human LD50 is, but extrapolating, 3 milligrams of fentanyl (about the weight of a sesame seed) would kill a full sized man half the time, and so it would take roughly 30 micrograms of carfentanil (half the weight of a grain of salt) to do the same.

The Russians used a carfentanil mist (delivered via the HVAC system, presumably) to incapacitate Chechen hostage takers in a Moscow theater in 2002. Clever, except it also offed 125 of the hostages from acute respiratory depression.