Russian spetsnaz security forces used a fentanyl analogue or derivative to incapacitate people rapidly in the Moscow theater hostage crisis in 2002 . The siege was ended , but about 130 of the 850 hostages died from the gas . The Russian Health Minister later stated that the gas was based on fentanyl , but the exact chemical agent has not been identified
Moscow theater hostage crisis
Moscow theater hostage crisis
Fentanyl