Updated: December 31, 2020 5:44 PM EST | Originally published: December 31, 2020 10:43 AM EST

(MADISON, Wis.) — Authorities arrested a suburban Milwaukee pharmacist Thursday suspected of deliberately ruining hundreds of doses of coronavirus vaccine by removing it from refrigeration for two nights.

The Grafton Police Department said the former Advocate Aurora Health pharmacist was arrested on suspicion of reckless endangerment, adulterating a prescription drug and criminal damage to property. The department said in a news release that he was in jail. Police did not identify the pharmacist, saying he has not yet been formally charged.

His motive remains unclear. Police said that detectives believe he knew the spoiled doses would be useless and people who received them would mistakenly think they’d been vaccinated when they hadn’t.

Advocate Aurora Health Care Chief Medical Group Officer Jeff Bahr told reporters during a teleconference Thursday afternoon that the pharmacist deliberately removed 57 vials that held hundreds of doses of the Moderna vaccine from refrigeration at a Grafton medical center overnight on Dec. 24 into Dec. 25, returned them, then left them out again on the night of Dec. 25 into Saturday. The vials contained enough doses to inoculate 570 people.

A pharmacy technician discovered the vials outside the refrigerator on Saturday morning. Bahr said the pharmacist initially said that he had removed the vaccine to access other items in the refrigerator and had inadvertently failed to replace it.

The Moderna vaccine is still viable for 12 hours outside refrigeration, so workers used the vaccine to inoculate 57 people before discarding the rest. Police said the discarded doses were worth between $8,000 and $11,000.

Bahr said health system officials grew more suspicious of the pharmacist as they reviewed the incident. After multiple interviews the pharmacist acknowledged Wednesday that he removed the vaccine deliberately and left it out overnight Dec. 24 into Dec. 25, returned it to the refrigerator at some point and then removed it again overnight Dec. 25 to Dec. 26.

Bahr said that means that the doses people received Saturday are all but useless. Moderna has told Aurora that there’s no safety concerns but the system is monitoring them closely, he said.

Bahr declined to comment on the pharmacist’s motive.

Contact us at letters@time.com.

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