The first murder Kürten definitively committed occurred on 25 May 1913. During the course of a burglary at a tavern in Mülheim am Rhein, he encountered a nine-year-old girl named Christine Klein asleep in her bed. Kürten strangled the child, then slashed her twice across the throat with a pocket knife, ejaculating as he heard the blood dripping from her wounds onto the floor by her bed.
Kürten freely admitted his guilt in all the crimes police had attributed to the Vampire of Düsseldorf, and further confessed he had committed the unsolved murders of Christine Klein and Gertrud Franken in 1913. In total, Kürten admitted to 68 crimes including 10 murders and 31 attempted murders. He made no attempt to excuse his crimes, but justified them upon the basis of what he saw as the injustices he had endured throughout his life. Nonetheless, he was adamant he had not tortured any of his child victims. Kürten also admitted to both investigators and psychiatrists that the actual sight of his victim's blood was, on many occasions, sufficient to bring him to orgasm, and that, on occasion, if he experienced ejaculation in the act of strangling a woman, he would immediately become apologetic to his victim, proclaiming, "That's what love is all about". He further claimed to have drunk the blood from the throat of one victim, from the temple of another, and to have licked the blood from a third victim's hands. In one of these instances, he had drunk so much blood from the neck wound he had inflicted upon victim Maria Hahn that he vomited. Kürten also admitted to having decapitated a swan in the spring of 1930 in order that he could drink the blood from the animal's neck, achieving ejaculation in the process.