Wikipedia: Tokyo Subway Sarin Attack

Aum Shinrikyo was founded in 1984 as a yoga and meditation class, initially known as Oumu Shinsen no Kai (オウム神仙の会 "Aum Mountain Hermits’ Society"), by pharmacist Chizuo Matsumoto.

Later, Matsumoto changed his name to Shoko Asahara and masterminded the most deadly terrorist attack in Japanese history. Asahara was executed by hanging on July 6, 2018, at the Tokyo Detention House, 23 years after the sarin gas attack, along with six other cult members.