Stanisław Modzelewski was born on March 15, 1929, in Szczepankowo, Poland.

Stanisław Modzelewski murdered several women between 1952 and 1967. His victims ranged in age from 18 to 87 years old. He strangled them, sometimes using a scarf or his bare hands. After killing, he took personal items and other objects from the victims, many of which he discarded. His actions were marked by extreme cruelty, and the murders had a sexual motive. The victims were often left with the lower parts of their bodies exposed, and the positions of the bodies indicated further sexual assault. It was noted that he displayed sadistic tendencies.

Modzelewski's first confirmed victim was Józefa Pietrzykowska, a 67-year-old woman he killed in a forest near Gałkówek in July 1952. Following her, he murdered Maria Kunka, a 32-year-old, in December 1952, also in a forest. He continued his killing spree with Teresa Piekarska, a 21-year-old, in March 1953, and Irena Bernadetta Dunajska, a 24-year-old, in January 1955. In March 1956, he killed an 18-year-old named Helena Walos, and later that year, in August, he murdered 22-year-old Helena Klata.

The investigation into these murders began but was closed in 1957. The police struggled to find Modzelewski due to misguided assumptions. They thought the murderer was connected to the Polish State Railways, as several crimes occurred near railway tracks. Fear spread in the community as no one knew who the killer was.

In 1967, the case reopened following the murder of 87-year-old Maria Gałecka in Warsaw. Investigators soon identified Stanisław Modzelewski as the prime suspect. He was known to have disputes with Gałecka, who was his neighbor at the time. Ultimately, he was arrested and charged with these murders.

Modzelewski faced trial and was convicted of seven counts of murder and three counts of attempted murder. He was sentenced to death and executed by hanging on November 13, 1969, in Warsaw.