in 2002 an insurgent group stormed a movie theater. They permitted the hostages to make emergency calls to their family and emergency services. The Spetsnaz forces showed up and took a lethal mixture of carfentanil and remifentanil and gassed it through the vents (or depending on who you ask a freshly drilled hole in the wall). This was meant to incapacitate the insurgents; however it reached the hostages and pretty much everyone was hurt by it. More people died because of the Spetsnaz than the insurgent group.
