He administered fatal doses of medication to the people in his care at two hospitals in northern Germany. Högel worked as a nurse at clinics in Oldenburg and Delmenhorst during the years of 1999–2002 and 2003–2005He is now said to have killed 36 patients in Oldenburg and 64 in nearby Delmenhorst between 1999 and 2005 Investigators say he may have killed even more but potential victims have been cremated. Högel was first caught in 2005 injecting unprescribed medication into a patient in Delmenhorst. In 2008 he was jailed for seven years for attempted murder. He told the court he had acted on impulse and apologised to the victims’ relatives.
In 2014-15, a second trial found him guilty of two murders and two attempted murders and he was given the maximum sentence. Police launched a major investigation in October 2014, after which 200 suspicious deaths were identified. More than 130 bodies in Germany, Poland and Turkey were exhumed. In January 2018, German prosecutors charged Högel with the murder of 97 patients. He admitted now killing at least one hundred. Dozens of relatives of those who died at the hands of Niels Högel were in court to hear his confession.