A German nurse already convicted of murdering several patients has now been found to have murdered at least 86 people under his watch.
Niels Högel admitted to intentionally inducing cardiac arrest by overdosing medication in 90 of his patients. He said he enjoyed trying to revive his patients, as reported by the New York Times.
The nurse was previously sentenced to life in prison in 2015 on two counts each of murder and attempted murder.
But during the trial he admitted he had killed many more by injecting patients' with a cardiovascular drug in order to then resuscitate them, which sometimes didn't work.
It was reported he chose his victims at random.
Chief police investigator Arne Schmidt told the Guardian there was evidence for at least 90 murders, and at least as many cases that could not be proven.
The crime "defied any scope of the imagination" chief of police Johan Kühme in the city of Oldenburg told the Times.
In late 2014 police went through evidence of more than 500 patient files, performing toxicology reports.
The total number could be greater still, but will remain unknown as some of the patient bodies were cremated.
The harrowing career of Mr Högel, who has been touted as Germany's worst serial killer, was reported as beginning with his first murder in 2000.
After killing at least 35 patients in Oldenburg, he moved to a hospital in Delmenhorst where within a week he killed a patient.
Mr Kühme noted Mr Högel had been given a clean reference which allowed him to move to the hospital and continue his murderous intent.
The murders could have been prevented, he said, "People at the clinic in Oldenburg knew of the abnormalities."
Using a vast array of drugs to induce a medical emergency, his behaviour didn't go unnoticed by fellow hospital staff, but was never reported on.
The number of deaths in the intensive care unit doubled while he was at the hospital, but no action was taken.
In 2005 Mr Högel killed his final patient by injecting the drug ajmaline. It was reported a fellow staff member who witnessed what would be his last lethal injection administered, but hospital management didn't act on it for two days.
Now six employees of at the hospital have been charged with negligent manslaughter for their failure to act.
Although already serving a life sentence, it's expected he will be tried on further charges based on findings from the investigation.