North Texas drug dealer who used darknet to sell fentanyl, elephant tranquilizer sentenced

Sean Shaughnessy , 55 , was convicted last year of conspiracy to possess and distribute illegal drugs.

He sold drugs including fentanyl, pentedrone, carfentanil and elephant tranquilizer.

Authorities linked drugs he sold to the overdose death of a man in his 20s .

He was caught through an undercover operation by Homeland Security .