Early one morning in October 2002, a dense white cloud silently filled Moscow's Dubrovka Theater.
It had been three days since Chechen militants took more than 800 people hostage. Russian special forces faced an impossible task: liberating the hostages from a theater laced with booby traps and several dozen suicide bombers. They turned to chemicals Russian scientists had been researching for years, and pumped an aerosol containing potent forms of the synthetic opioid fentanyl into the theater before storming it.
As the mysterious substance descended, people knelt, covering their faces as best they could, according to eyewitness accounts. No one was choking. People simply dropped into what seemed to be a deep sleep.
"I lay down and started praying," said Vladimir Stukanov, the director of the children's troupe at the theater. His friend, Boris Lapin, had given him his coat, which Stukanov pressed to his face. "Boris died, but saved me," he said.
Commandos stormed the theater and killed the attackers, but more than 120 hostages died from the effects of the chemicals. Many survivors suffered lasting health effects.
The Russian government acknowledged that the aerosol contained fentanyl-related compounds, but refused to reveal the exact composition. Years later, British government scientists tested clothing and urine samples from three survivors and concluded that the aerosol contained carfentanil, one of the most potent opioids on the planet, as well as the less-powerful remifentanil.
Today, carfentanil is readily available from vendors in China, who offer to export the deadly substance around the world, no questions asked, a href='https://apnews.com/7c85cda5658e46f3a3be95a367f727e6/Chemical-weapon-for-sale:-China's-unregulated-narcotic'an Associated Press investigation has found/a. Carfentanil is not a controlled substance in China, the world's largest chemicals exporter, despite U.S. efforts to get Beijing to blacklist it.
Olga Dolotova, an engineer, remembers seeing the plumes descend in the theater before losing consciousness. Later, she heard someone say, "She is alive." When Dolotova opened her eyes again, she found herself on a bus packed with bodies.
"It was such a horror just to look at it," she said. "Nobody was moving. They put the people there like dolls."
Dolotova wanted to get up, or shout. She wanted the bus to stop. And she badly needed to vomit. "I was having spasms, but I could not throw up," she said. When she reached the hospital, she gulped down some tea and began retching. "I continued throwing up and throwing up and throwing up," she said.
She said she understands why Russian special forces used the chemicals. "They had to somehow render them immobile," she said of the militants. "What else was there?"
But she said medical and rescue personnel were not trained to deal with effects of the mysterious gas and made deadly errors — failing, for example, to tilt people's heads so they didn't choke on their own tongues. "More people would have been saved," she said.
The aerosol created a kind of sleep without memory, Stukanov said.
"It's like this cluster has been erased and dropped out of your head," he said.
Danilova reported from Washington. AP reporter Iuliia Subbotovska, video journalist Veronika Silchenko and news assistant Sergei Fedotov in Moscow contributed to this report.