An Ohio doctor has been charged with over two dozen counts of murder for allegedly prescribing potentially fatal doses of opioids to critical-care patients, prosecutors announced Wednesday.

William Husel, 43, was indicted on 25 counts of murder by a Franklin County grand jury following a six-month criminal investigation into the deaths of dozens of patients over a four-year period at Columbus’ Mount Carmel Health System.

Prosecutors allege that Husel, who has since been fired, ordered excessive amounts of painkillers without “any legitimate medical purpose,” often forcing intensive-care nurses “to override the hospital’s medication-dispensing cabinets to access such high doses.”

Husel turned himself in to authorities around 10:30 a.m. He’s now facing 15 years to life in prison for each murder charge. It remains unclear why Husel overprescribed the painkillers.

“This breach of the doctor’s oath is vile,” Columbus Police Chief Tom Quinlan said at a press conference announcing the charges on Wednesday.

Prosecutors allege Husel ordered excessive doses of fentanyl, ranging from 500 micrograms to 2,000 micrograms, for 34 patients. Six of the patients did not die from the high doses, authorities said. The typical dose of the opioid is between 25 and 100 micrograms.

The 25 Mount Carmel patients who died ranged in age from 37 to 85, and were seeking treatment for a variety of issues, including trouble breathing and cancer. In many instances, relatives had already given doctor’s permission not to resuscitate their family members.

“At the 500 microgram level there would be no legitimate medical purpose,” Franklin County Prosecutor Ron O’Brien said on Wednesday. “The only purpose would be to hasten their deaths.”

Husel was a critical-care doctor with the Mount Carmel Health System, one of the largest in central Ohio, from 2015 to 2018. He was suspended on Nov. 21, 2018, and fired two weeks later.

The State Medical Board of Ohio suspended Husel’s medical license in late January, citing his “failure to meet acceptable standards regarding the selection of drugs, violations of the minimal standards of care and failing to cooperate in a board’s investigation.” Husel had previously been granted a July hearing date to appeal the medical board’s decision.

“Mount Carmel has made and will continue to implement meaningful changes throughout our system to ensure events like these never happen again,” Hospital CEO Ed Lamb said in a statement after Husel’s arrest. “There is nothing more important to Mount Carmel than the safety of our patients and their trust in us. Our thoughts and prayers continue to be with the families of patients affected by this tragedy.”

The former doctor is also embroiled in over a dozen wrongful death lawsuits since January. In one suit, the family of 82-year-old Melissa Penix alleges she admitted herself to Mount Carmel West in November after suffering from “stomach pains.”

She died about five minutes after Husel gave her 2,000 micrograms of fentanyl, the lawsuit alleges. Husel allegedly told Penix’s family that she was brain dead and “encouraged them” to end her care. In Ohio, physician-assisted deaths are illegal.

Husel’s attorney, Greg Foliano, could not immediately be reached for comment.