FILE PHOTO: Former nurse Niels H. (L) masks his face with a folder with the help of his lawyer Ulrike Baumann on his arrival in the courtroom at the regional court in Oldenburg, December 9, 2014. REUTERS/Fabian Bimmer

BERLIN (Reuters) - German public prosecutors on Monday said they had brought new charges against a killer nurse already serving a life sentence for murdering two patients, accusing him of killing another 97 people with lethal injections.

If found guilty, it would make him Germany’s deadliest serial killer.

The man, identified only as Niels H. under reporting rules, has admitted to deliberately injecting patients at two clinics in northern Germany with deadly drugs and then trying to revive them in order to play the hero.

Prosecutors in the northern German city of Oldenburg said an investigation and toxicology reports showed that the accused also gave 35 people at a clinic in Oldenburg and 62 at one in nearby Delmenhorst life-threatening medicines.

Prosecutors said Niels H. should have been aware that the drugs he was giving his patients could cause ailments ranging from possible cardiac arrhythmia, ventricular fibrillation to hypotension.

“From the prosecutorial point of view, the accused Niels H. accepted, at least tacitly, in all cases the death of the patients due to the effects of the drugs,” the prosecutors said in a statement.

The new charges come in addition to two counts of murder for which an Oldenburg court sentenced him to life in prison in 2015.

Ten years ago, a German nurse was convicted of killing 28 elderly patients. He said he gave them lethal injections because he felt sorry for them. He was sentenced to life in prison.

In Britain, Dr. Harold Shipman was believed to have killed as many as 250 people, most of them elderly and middle-aged women who were his patients. Known as Dr. Death, Shipman was sentenced to 15 life terms in 2000; he died prison in 2004, apparently a suicide.