Authorities in Russia released gas into Moscow’s Dubrovka Theater during the 2002 hostage crisis. Chechen militants seized the theater on October 23, 2002, while the audience was watching the musical Nord-Ost, taking roughly 900 people hostage.
After a siege lasting several days, Russian security forces pumped an incapacitating chemical agent into the building’s ventilation system before storming it. The operation killed all 40 hostage-takers, but many hostages also died from the gas, its effects, or inadequate emergency treatment. The question’s figure of 116 is often found in early reports; later accounts generally give the hostage death toll as 132.
The exact chemical was not immediately disclosed. Russian officials described it as fentanyl-based, while later analysis suggested a mixture involving powerful synthetic opioids. The crisis remains controversial because survivors and human-rights investigators criticized the secrecy surrounding the agent and the rescue’s medical response. The incident is also called the Moscow theater hostage crisis or Nord-Ost siege.