Václav Mrázek was born on October 22, 1925, in Svinařov, Czechoslovakia. He was one of twelve children in a poor family, but four of his siblings died young. Due to their financial struggles, the family even had to sleep in a railroad car at one time. Mrázek's education ended in the fifth grade of primary school. After that, he and his brother Karel began stealing food and clothing with their parents' knowledge. Mrázek's father made him teach their younger siblings how to steal as well.

In 1941, Mrázek was caught for one of these thefts. He received a conditional sentence and spent 18 months in prison. Upon his release, he wanted to become a police officer or soldier, but he was not accepted because he was small in stature. In 1946, he enlisted as an armed escort for a humanitarian convoy to Romania and Bulgaria. During this time, he claimed to have witnessed soldiers looting supplies and exchanging goods for sexual favors. These experiences deepened his interest in sadistic pornography.

As he grew older, his sexual desires became troubling. At one point, he attempted to break into a morgue, seeking to have sex with a corpse. He also reported that feeling his immobilized victims was exciting. Despite these desires, he had relationships with partners who found him average and somewhat repulsive, particularly because of his thriftiness stemming from his upbringing. During this time, Mrázek had a long-term partner and several children.

Václav Mrázek committed his first known murder on August 22, 1951, when he killed 15-year-old Hana Chloubová by beating her to death with a stick. Afterward, he dragged her body to a secluded place and sexually assaulted it.

On September 16, 1951, he shot and killed 32-year-old Bronislava Pajúrková on a road between Jirkov and Kyjice. He then disposed of her body in a stream after sexually assaulting it. Following this, Mrázek used a knife for his next two attacks. Both victims survived; one suffered a knife wound to the jaw, and the other sustained 18 shallow stab wounds, which misled investigators into thinking a woman might have been the attacker.

On June 1, 1952, Mrázek shot at 19-year-old Elena Mermanová three times. Although she was hit by bullets, she survived. However, his assault left her shaken. The next day, she discovered the body of 16-year-old Marie Dvořácková in an area Mrázek had taken her. He had shot Dvořácková while she waited for her friends. Afterward, he sexually assaulted her body.

On July 14, 1954, Mrázek shot and killed 16-year-old Jiřina Helmichová after she passed by him in the forest. He then sexually assaulted her body as well. His next crime occurred on August 9, 1955, when he killed a couple: 26-year-old Karel Trlifaj and 19-year-old Libuše Dufková. He shot Trlifaj multiple times and then killed Dufková after she attempted to pretend to be dead. He had also sexually assaulted her body.

Mrázek's pattern of violence escalated. He attempted to strangle several women but they escaped. He also began raping very young girls, some as young as six. He did not kill these victims, as he deemed it unnecessary. On November 9, 1956, he murdered Alžběta Beran with an axe during a burglary, then later raped her 11-year-old daughter, Jarmilla.

He evaded capture for a long time despite extensive investigations. He was finally apprehended on March 17, 1957, during a police inspection after being reported for theft. A search of his home uncovered stolen items and a gun linked to the murders. After learning about the ballistic evidence, Mrázek confessed to his crimes.

He was convicted of seven murders, four attempted murders, and 14 rapes. Mrázek was sentenced to death and hanged on December 29, 1957. His execution marked the end of a series of brutal crimes that terrorized the region.