He was convicted of possessing 30 grams of carfentanil while on parole for his previous conviction. A lethal dose of carfentanil is 2mg, so it was at least 15,000 doses.
1. https://www.doj.nh.gov/news/2017/20171011-preston-thorpe-sen...
1. https://www.doj.nh.gov/news/2017/20171011-preston-thorpe-sen...
Ah, I see from your link it was u-47700 he was arrested with. Certainly a potent and potentially lethal substance, but not exactly on the same scale as carfentanil. U-47700 is quoted as 7.5x the potency of morphine, fentanyl at 50-100x and carfentanil around 4000
I guess it was the next logical step in the "smaller quantities of more powerful stuff are easier to smuggle" race, but I'd expect to see more dealers turning up dead from accidental exposure if it became widespread.