Niels Högel, a 42-year-old nurse in Germany, was found guilty of murdering 85 of his patients on Thursday and sentenced to life in prison. 

Authorities say while Högel was working at clinics in the northern German towns of Delmenhorst and Oldenburg between 2000 and 2005, he injected deadly doses of drugs on his patients to induce cardiac arrest so that he could show off his resuscitation skills but failed to bring back dozens of patients. Officials suspect that he may have killed as many as 300 patients. He is considered the most prolific serial killer in the history of peacetime Germany, and perhaps in the world, according to the New York Times. Högel is already serving a life sentence from February 2015 for two murders and several attempted murders of intensive care patients at another hospital. On Thursday, the judge called his crimes “beyond comprehension” and sentenced him to the most severe form of life sentence possible under German law, which doesn’t allow for the usual possibility of parole after 15 years, according to DW. Högel had apologized to the victims’ families on Wednesday, saying that he would like to “sincerely apologize for what I have done to each and every one of you” and that he had come to realize the amount of suffering his “terrible deeds” had caused, according to the Guardian