Original sentence: An incapacitating agent of some kind was used by the Russian authorities in order to subdue the Chechen separatists who had taken control of a crowded theatre.Kolokol-1 is thought to be the chemical agent employed by a Russian Spetsnaz team during the Moscow theatre hostage crisis in October 2002.The chemical agent used in the Moscow theatre hostage crisis has never been definitively revealed by the Russian authorities, though many possible identities have been speculated
Edited sentence: Kolokol-1 is thought to be the chemical agent employed by a Russian Spetsnaz team during the Moscow theater hostage crisis in October 2002