German prosecutors on Thursday suggested Niels Hoegel, a male nurse already serving a life sentence for two murders, could be responsible for over 100 deaths. The criminal is set to face new charges next year.

Hoegel, 41, served in clinics in northern Germany before his sensational crime came to light two years ago. To get rid of "boredom" and gain the feeling of euphoric, Hoegel persecuted his patients – failed to save them many times. He testified that he injected patients with lethal drugs to impress his colleagues by showing off his – as he described – "excellent" resuscitation skills on the agonal people.

Convicted of two murders, two attempted murders and harming patients, Hoegel was detained in February 2015. He then admitted to the court he had killed dozens of patients in later trials, which led to an extended investigation.

Detectives exhumed some 130 bodies from 67 cemeteries, reviewed hundreds of patient files and hospital records, and questioned the killer six times. Toxicology studies continue as investigators believe already that Hoegel cannot walk away clean from 38 killings in Oldenburg hospital and 62 in Delmenhorst between 1999 and 2005 – not to mention the suspicious cases yet to be examined. 

Should he found guilty to all the deaths, he would become one of the worst serial killers in Germany’s post-war history.

The records at the Oldenburg suggested the death rate and resuscitations had risen when Hoegel was on shift, reports BBC citing a German magazine. But it did not come into his way when Hoegel got a subtle reference to apply for his next job at Delmenhorst’s hospital. Number of dying patients dramatically increased during his shift in Delmenhorst as well.

The chief police investigator in charge of Hoegel’s case, Arne Schmidt, described the death toll "unique in the history of the German republic" and clarified the murderer had killed "without a discernible pattern," only those in serious condition.

During his trial in 2015 Hoegel said he was "honestly sorry", confessed his crimes were "relatively spontaneous." He said he tried to resist the impulse each time he killed someone but his determination would fade gradually.

Hoegel is referred as Niels H. in the country due to reporting restrictions. It is forbidden to publish the image of his face under the country's privacy laws.

Hoegel was raised in a Catholic family, which he described to his court-appointed psychiatric expert Konstantin Karyofilis as "warm-hearted and sustainable," Daily Mail said. His father was a nurse, a staunch supporter of Germany’s Social Democratic Party and his mother ended up as a cleaning lady although she was trained as a lawyer’s assistant. Hoegel has an elder sister working as a dental assistant. The family was "helpful, kind and caring," according to the depicture from a neighbor.

Straight-A student Hoegel suffered his first trauma at 11 when his parents briefly split. He decided to become a firefighter at 16, failed by his vertigo then wished to become a doctor but found the study too difficult. Hoegel dropped out of school before attempting for college, then got his nurse training when he was 17. After qualified in medical attention in 1999, he struggled with the nursing work early on, described his first-time experience assisting a surgery as a "traumatizing experience," and developed depression on it.

He carried out his first known murder in February 2000, failing to revive the patient he injected.

It is believed Hoegel was suffering from a rare condition known as  Munchausen by Proxy syndrome, which involves causing harm to act as an angel of salvation.

Ten years ago, another German nurse was convicted of killing 28 elderly patients. He said he felt sorry for them so he got them injected with lethal drugs.

(Source: Agencies)