It happened quickly.
Just three years ago, fentanyl was only being blamed for a few dozen deaths a year. It's unclear what triggered such a dramatic change, but in the past few years international drug cartels came to the realization that fentanyl was their dream drug.
It's incredibly addictive and up to 50 times as powerful as street-grade heroin. And it's cheap and easy to manufacture, making it ideal for transportation.
"A first class envelope of the stuff could get the entire county high," said Al Della Fave, spokesman for the Ocean County Prosecutor, in a recent interview.
Not only that, unlike other opioids, which have a natural component, it's completely synthetic. That seemingly minor quirk allows black market laboratories in places like China to tweak its chemical makeup slightly, creating dozens of analogues that maintain the original potency but are technically different drugs that can be imported to the United States.
The toxic combination caught public health officials, already struggling with a burgeoning heroin crisis, off-guard, and left law enforcement scampering to adjust.