Jan. 22 (UPI) -- A former German nurse who's already behind bars serving a life sentence was charged Monday with killing 97 more patients in two hospitals.
Niels Hoegel was jailed in February 2015 for two deaths and several attempts to kill intensive care patients at the Delmenhorst hospital in northern Germany,
New charges against Hoegel include 62 additional killings at Delmenhorst and 35 charges relating to the deaths at a facility in Oldenburg, where Hoegel worked from 1999 to 2002.
Authorities said the nurse would give patients heart medication and other drugs, and prompt overdoses and cardiac crises so he could be the one to resuscitate them.
Prosecutors said they looked into 500 patient files, finding that Hoegel may have killed more than 100 patients in a span of several years.
Prosecutor Martin Koziolek said three suspicious cases didn't produce enough evidence to the list of killings.
Koziolek believed Hoegel "in all cases at least accepted the death of the patients as a result of the effect of the drugs."
Detectives researching the case exhumed 134 bodies from 67 separate cemeteries and questioned the former nurse six times throughout the investigation.
Any additional convictions against Hoegel would only affect his possibility of parole, as consecutive sentences are not part of Germany's legal system.
An investigation into neglect at the hospital is ongoing.