Italian police have arrested a nurse suspected of killing at least 38 of her patients because they, or their relatives, were irritating her. The officials also found a selfie, with the nurse giving a thumbs-up in front of a recently deceased patient.

Daniela Poggiali, 42, a hospital nurse was arrested in her native town of Lugo in the northern Italian region of Emilia-Romagna, a province of Ravenna, reported Corriere della Sera, an Italian daily newspaper.

The police suspect her of the murder of an elderly patient, Rosa Calderoni, 78, who was taken to hospital with a routine illness. Tests showed that Calderoni died of an injection of potassium chloride, a medical substance, which can trigger cardiac arrest.

Potassium leaves no traces in the patient’s bloodstream after a few days and it makes it more difficult to investigate the case, the prosecutors told Corriere della Sera.

#DanielaPoggiali: l'infermiera che uccide una paziente e si fa il selfie con il cadavere http://t.co/c4h9GCUymGpic.twitter.com/sPhFbNFdpk — SuperstarZ (@SuperstarZ9000) October 14, 2014

The investigation revealed that the nurse was not only culpable of Calderoni’s death but also the deaths of at least 38 patients. All of them were reportedly murdered in 2014. At least 200 witnesses gave testimonies against ‘the worst nurse.’

Police officers also found a scandalous selfie of the nurse smiling and giving a thumbs-up in front of a recently deceased patient, Chief Prosecutor Alessandro Mancini told a press conference.

“I can assure you in that in all my professional years of seeing shocking photos, there were few such as these,” added Manchini, adding that the nurse was “unperturbed” during her arrest.

"When we went to arrest her, she was silent, impassive," he said.

One of the nurse’s colleague spoke of her as a "cold person but always eager to work."

Other medical personnel at the hospital added that they suspected her of giving the patients doses of laxatives, drugs that facilitate or increase bowel movements, at the end of her shift. They said Poggiali did this to annoy and embarrass them.

"We wondered whether these deaths could be so frequent without anyone doing anything," a co-worker told Corriere della Sera.