At least one patient and as many as ten died after a nurse injected them with tap water instead of the fentanyl they were prescribed, report NBC News affiliates in Oregon, and they suffered infections due to the unsterilized source. Police are investigating the deaths and the implication is that the nurse was diverting, i.e. stealing the drugs.
A brief statement: "We were distressed to learn of this issue. We reported it to law enforcement and are working closely with them." No-one has been arrested or charged with anything, but it's surely coming.
The further thought that the perpetrator might have gotten away with it if they'd used clean water doesn't go anywhere pleasant.