PORT WASHINGTON, Wis. (AP) — A Wisconsin pharmacist told police he tried to ruin hundreds of doses of coronavirus vaccine because he felt the shots weren’t safe, a prosecutor said Monday.

Police in Grafton, about 20 miles north of Milwaukee, arrested Advocate Aurora Health pharmacist Steven Brandenburg last week following an investigation into the 57 spoiled vials of the Moderna vaccine, which officials say contained enough doses to inoculate more than 500 people.

“He’d formed this belief they were unsafe,” Ozaukee County District Attorney Adam Gerol said during a virtual hearing. He added that Brandenburg was upset because he was in the midst of divorcing his wife, and an Aurora employee said Brandenburg had taken a gun to work twice.

Gerol didn’t explain why Brandenburg thought the vaccine wasn’t safe. Federal regulators authorized the Moderna vaccine for emergency use on Dec. 18. According to the U.S. Food and Drug Administration, the vaccine’s side effects are mostly mild, ranging from soreness at the injection site to nausea and fever.

Charges are pending and the FBI and U.S. Food and Drug Administration are also investigating.

Advocate Aurora Health Care Chief Medical Group Officer Jeff Bahr has said Brandenburg admitted that he deliberately removed the vials from refrigeration at the 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.

A pharmacy technician discovered the vials outside the refrigerator on Dec. 26. Bahr said Brandenburg initially said he had removed the vials to access other items in the refrigerator and had inadvertently failed to put them back.

The pharmacist has been fired.

The Moderna vaccine is 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 the doses people received Dec. 26 are all but useless. But Gerol said during the hearing that Moderna would need to test the doses to make sure they’re ineffective before he can proceed with any charges beyond destruction of property.

Judge Paul Malloy set a $10,000 signature bond for Brandenburg and ordered him to surrender all his firearms to sheriff’s deputies, not to work in the health care field and to have no contact with Aurora employees.