He was first reprimanded for committing lecherous acts with girls,[b][citation needed] spending a total of 12 years behind bars.
After leaving Wronki Prison, Kwaśniak began a series of thefts, rapes and murders of young boys.
Under the pretence that he had received an envelope from the 10-year-old victim's father, Kwaśniak managed to enter the child's apartment.
The boy was strangled with a towel; found next to him was a card with the inscription "Finally, I made the expected revenge -B."
The police in Poznań collected details from previous murders and commissioned sexologist Lechosław Gapik to develop a psychological portrait of the perpetrator.
The issue was publicized by the "997" publivision program, which reconstructed the murders and gave the perpetrator a modus operandi and portrait.
Thanks to these actions, it was established that the perpetrator had accosted boys in Rataje for a few days, with whose help a facial composite was made and published by the media, as well as being posted at bus stops and in taxis.
Under the pretext of giving the parents of the boy a letter from his aunt who lived abroad, he managed to enter the apartment.
He also admitted to several dozen apartment thefts, including those in Słupsk, Białystok, Lublin, Kraków, Częstochowa, Bydgoszcz, Szczecin and Wejherowo.