Petr Zelenka was born on February 27, 1976, in the Czech Republic.

Petr Zelenka, a nurse, committed his crimes at a hospital in Havlíčkův Brod from May to December 2006. He used a hidden vial of heparin, a drug that thins the blood, to kill his victims. Zelenka administered lethal doses of this drug to seven patients, resulting in their deaths. He also attempted to kill ten others during this time.

Zelenka's actions appeared to be driven by a desire to test the medical staff in the hospital. He believed they were not competent enough to uncover the truth about his actions. This belief influenced his decisions and methods.

In February 2008, Zelenka was found guilty of murder and attempted murder. He received a life sentence for his crimes. His case raised many questions about hospital safety and the responsibilities of medical staff.