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. ​

The killings began on August 7, 2000, with the disappearance of Afsaneh Karimpour, a 30‑year‑old mother. Just days later, more bodies began appearing — including those of Layla (August 10) and Fariba Rahimpur (August 11). As police struggled to connect the cases, Hanaei continued his spree with brutal consistency, killing at least 16 women over the following year. Many of the victims were found wrapped in veils or burlap sacks, indicating premeditation and ritualistic behavior. In one instance, three women, Maryam Beygi, Shiva, and Zahra, were found together on July 3, 2001, suggesting a possible escalation in his confidence and boldness.

Hanaei’s murders created widespread panic in Mashhad. Because the city is home to the Imam Reza shrine, one of Shia Islam’s most important pilgrimage sites, the killings attracted significant media attention and public outrage. Yet, in a shocking twist, Hanaei also garnered support from some religious hardliners who praised him as a vigilante “cleansing” the city. Conservative newspaper Jomhuri Islami defended his motives, rhetorically asking, “Who is to be judged? Those who eradicate the sickness or those who stand at the root of the corruption?”

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.