Born in 1960, Waltraud Wagner was a nurse's aide at the Geriatriezentrum am Wienerwald in Lainz, Vienna. She began working there in her early twenties and was known for her charisma and leadership qualities. Wagner's initial act of murder in 1983 was reportedly at the request of a patient seeking relief from suffering. 

Wagner's first murder involved administering a lethal dose of morphine to a patient. Realizing the control she wielded over life and death, she recruited three other nurse's aides: Maria Gruber, Irene Leidolf, and Stephanija Meyer. Together, they developed a method of drowning patients by pouring water into their mouths while pinching their noses, a technique they cynically referred to as "mouth care." This method was difficult to detect, as fluid in the lungs was common among elderly patients. Over six years, the group confessed to 49 murders, though estimates suggest the number could be as high as 200. In 1991, Wagner was convicted of 15 murders, 17 attempted murders, and two counts of assault, receiving a life sentence. She was released from prison in 2008 due to good behavior.​