Serhiy Fedorovych Tkach was born on September 15, 1952, in Kiselyovsk, Kemerovo Oblast, in the Soviet Union. He grew up in a time when the country was changing and faced many challenges. Tkach served in the Soviet Army, and he sometimes told his neighbors that he was a veteran of the Soviet-Afghan War, although this claim was not verified.

After leaving the army, Tkach became a police investigator in Kemerovo Oblast. He was good at his job and was even recommended to attend a Ministry of Internal Affairs school. However, his career took a turn for the worse when he was caught falsifying evidence. As a result of this misconduct, he was forced to resign from the police force.

Following his resignation, Tkach held various jobs. In 1982, he moved to the Ukrainian SSR, where he continued his career as a police investigator in Dnipropetrovsk Oblast.

In 1984, Serhiy Tkach began his pattern of crimes in eastern Ukraine. He targeted young women and girls, aged between 8 and 18. Many of these victims went missing across Dnipropetrovsk Oblast, Kharkiv Oblast, Zaporizhzhia Oblast, and Crimea. Tkach used his background in police investigations to cover his tracks. He would choose locations near railway lines that had recently been treated with tar, which helped him throw police dogs off his scent.

By August 2005, Tkach attended the funeral of one of his victims. Witnesses, including children, recognized him as someone who had been with the victim shortly before her death. Tkach was arrested at his home in Polohy. During the investigation, he confessed to numerous killings and claimed to have murdered over 100 people. He asked for the death penalty.

After a lengthy trial in 2008, he was convicted of killing thirty-seven women and girls over a span of more than two decades. His actions led to over fifteen wrongful imprisonments, including the suicide of one innocent man. Tkach was sentenced to life in prison for his crimes.

While he was in prison, Tkach fathered a child with a woman who had become interested in him after reading an interview. They married in 2015. Tkach served his sentence until he died of heart failure on November 4, 2018, in Prison No. 8 of Zhytomyr. He was buried by prison staff on November 7, as no family members came to claim his body.