Niels H. arrives for his trial at court on Nov. 27, 2014, in Oldenburg, Germany.

Update — Feb. 26, 8:39 a.m. ET: German male nurse Niels H. was sentenced to life in prison on Thursday for killing two patients, Agence France-Presse reported.

A German male nurse who admitted to killing at least 30 patients between 2003 and 2005 apologized to the victims' families in court Thursday.

Identified only as Niels H. due to Germany's strict privacy rules, the man has been on trial in an Oldenburg court since September for the alleged murders of three patients.

Though a court-appointed psychiatrist said earlier this month that Neils H. had admitted to killing at least 30 patients in his care, prosecutors believed the full number could be over 100 people.

According to the expert, Niels H. admitted to injecting seriously ill patients with an overdose of a potentially dangerous medicine so that he could resuscitate them.

In court on Thursday, the former nurse apologized for his actions.

"I am honestly sorry," the 38-year-old said, according to AFP. "Usually the decision to do it was relatively spontaneous."

Niels H. reportedly told police after he was arrested that he killed the patients because "he was bored." Prosecutors also said that he wanted to practice his "excellent" resuscitation skills, Deutsche Welle, a German broadcaster, reported in November.