YOKOHAMA--An 88-year-old man poisoned to death here in 2016 was one of many patients administered with an antiseptic solution at specific times by an ex-nurse because she wanted to avoid facing bereaved families, according to investigative sources.

Ayumi Kuboki confessed that she poisoned patients who were seriously ill over a period of two months in 2016, the sources said.

Kuboki, a resident of the city’s Tsurumi Ward, said during police questioning before her arrest that she targeted patients in serious condition who she thought were likely to die during her shift.

She allegedly accelerated their deaths to avoid the task of explaining the circumstances of the patients’ deaths to relatives falling on her, which she said to police was “troublesome.”

Kuboki, 31, was arrested on July 7 on suspicion of poisoning Sozo Nishikawa with an antiseptic solution at Oguchi Hospital in Yokohama’s Kanagawa Ward on Sept. 18, 2016. His blood samples showed a surface-activating agent component in high concentrations. The agent is contained in benzalkonium chloride, an antiseptic solution.

However, police are not convinced by Kuboki’s claims that she targeted only very sick patients.

Among the patients who died during the period in question were those whose health conditions were not that serious, according to the sources.

In the case of Nishikawa, Kuboki allegedly snuck into the patient’s room right before her night shift began on Sept. 18, 2016.

Nishikawa, who lived in Yokohama’s Aoba Ward, died after his condition took a sudden turn for the worse immediately after Kuboki entered his room. His heart rate began dropping around 4:50 p.m., and he died at 7 p.m.

Kuboki had arrived at the hospital at around 3 p.m. that day to prepare for the night shift, which started at 5 p.m., according to the sources.

But when Nishikawa died, a nurse who had taken care of him during the day shift was still in the hospital and broke the news of his death to his family.

Police believe that Kuboki administered the antiseptic solution to Nishikawa between 3 p.m. and 4:55 p.m.

Nurses worked in pairs during hospital shifts. Kuboki apparently entered Nishikawa’s room while another nurse on the night shift was being briefed by a nurse they were taking over from the day shift.

They are investigating how she administered the antiseptic solution, according to the sources.

Nishikawa was on an intravenous drip, but police believe that he was poisoned by the administration of a large amount of antiseptic solution over a short period of time, rather than injection via a drip.