Although he was once employed as a butcher, Grossmann preferred to earn his living by begging on the streets, and used some of his income on prostitutes who shared his bed most nights. By the early 1900’s, he began renting a squalid top floor apartment at 88/89 Langestrasse, located in the slums of the capital, that was situated near the last stop of the Silesian railway. He was considered bitter and secretive by his neighbours, but was given his privacy by his landlord because he always paid his rent on time. Through his begging he was earning enough money to pay for a regular housekeeper for his Berlin apartment, however these housekeepers invariably did not last long, and soon another applicant was sought to replace the previous young woman.
It is unknown when he began to murder women, but during World War I, Grossmann sold meat on the black market and later owned a hot dog stand at a train station near his home. It was strongly believed he used the flesh from his victims as meat substitute which he sold to the unsuspecting public and threw the bones and other inedible parts into the river. He would often invite prostitutes to his apartment for sex, whilst homeless women were offered food for the same arrangement, as well as advertising for single women to work for him who were all then butchered, before he disposed of the remains. This led to a spate of missing persons cases beginning in May 1918 when several bodies began showing up in the Luisenstadt Canal and Engelbecken Reservoir in various stages of decomposition.
In October 1920, 33-year-old Freida Schubert went missing. She had travelled to Berlin from Dresden, and on the day of her disappearance she had been seen propositioning many men, when one eventually accepted her services. Between October 7/9, 1920, the remains of a young women were found in the Luisenstadt Canal, which were later identified as those of Freida Schubert. On 16 October the Berliner Morgenpost reported that the killer had sawn through her bones with such brutality that he arm had been pulled from the shoulder and her heart had been pulled from her ribcage.
The police believed it was the work of a sadist and began by questioning any potential witnesses, one of whom said they saw the young woman in the company of Carl Grossmann. Police then made a search of his apartment on October 21, and found the missing woman’s handbag, however Grossmann was able to offer an innocent and plausible explanation and the matter was pursued no further. In December 1920, a young woman known as Melanie Sommer vanished, and the rash of unexplained disappearances and bodies discovered by police continued throughout 1921 right up to early August, when Elisabeth Barthel disappeared which saw the number of cases of missing women reported to the Berlin Police Department rise up to twenty three.
Grossmann’s trial began on 02 July 1922 and the prosecution had arraigned 17 witnesses to appear and testify against the defendant. Amongst these women was a prostitute named Erika, who went to Grossmann’s apartment but found it was too squalid and considered Grossmann himself to be too creepy and refused to complete the agreed sexual transaction. Some of these women had survived his sexual abuse and escaped with their lives, such as an unemployed industrial worker who accepted his offer to work as his housekeeper in August 1921. She began work immediately but was drugged and raped soon after. Despite consistent reports by numerous women, Grossmann’s defence counsel attacked the veracity of their claims and presented their stories as implausible.
Another witness, known was Helene was accused by Grossmann himself of having known about the murders and attempting to blackmail him. The prosecution presented to the court a long list of 23 women who had disappeared. Amongst the names of some of the missing women who were suspected of having fallen victim to Grossmann’s sexual depravity included Marie Feld, Luise Werner, Lisbeth Potske, Frieda Thomas, Emma Boritzki, Albertine Asher, 19-year-old Emma Baumann from Mecklenburg and a woman known only as Martha from Poland. Although Grossmann was not accused of direct complicity in the disappearances of these women, it was considered very likely he was responsible.
Carl Grossmann is often associated with other German killers of the Weimar period, such as Peter Kurten, Fritz Haarmann and Karl Denke.