Saeed Hanaei was born in 1962 in Mashhad, Iran. He worked as a construction worker and was known to be a devout Muslim. Hanaei lived with his wife and three children in Mashhad, Iran's holiest city. He served as a volunteer during the Iran-Iraq War. 

Between August 2000 and July 2001, Saeed Hanaei targeted female sex workers in Mashhad. He would lure them to his home under the pretense of offering services, especially when his family was away. Once there, he strangled them using their own headscarves. After the murders, he wrapped their bodies in chadors (traditional Iranian garments) and disposed of them in public areas, including streets and open sewers. ​

Hanaei justified his actions by claiming he was on a divine mission to cleanse the city of moral corruption, specifically targeting those he viewed as contributing to societal decay. His actions garnered mixed reactions; while many condemned his crimes, some religious extremists saw him as a vigilante addressing moral issues. ​

His arrest on July 25, 2001, came after a victim managed to escape and report him to the authorities. In September 2001, he was convicted of 16 murders and sentenced to death. Hanaei was executed by hanging on April 8, 2002, in Mashhad.