The chief executive of an Ohio health care system announced his resignation and the termination of 23 employees Thursday, one month after a doctor who worked for the hospital was charged in one of the largest murder cases in the state’s history.

Ed Lamb, the chief executive of Mount Carmel Health System, said in a statement that his resignation would take effect July 25. He added that the hospital’s executive vice president, Richard Streck, would be retiring at the end of September. The employees’ terminations were effective immediately.

“Mount Carmel will continue to work on strengthening our culture of safety,” Lamb said in the statement.

Eleven additional employees not included in the terminations will have the opportunity to return after additional training, Lamb said. Trinity Health, the hospital’s parent organization, will soon appoint an interim chief, he added. Mount Carmel describes itself as the second-largest health care system in central Ohio.

On June 5, Dr. William Husel, who served patients at hospitals in and around Columbus, was charged with killing 25 people over a four-year period by prescribing fatal doses of fentanyl.

Fentanyl, an opioid, is 50 to 100 times as strong as morphine, according to the Centers for Disease Control and Prevention.

Husel, who started working at Mount Carmel in 2013, first jeopardized the safety of critically ill patients in 2015, according to the State Medical Board of Ohio. During the next four years, potentially fatal doses of the medication were given to 29 of Husel’s patients, including five who still had a chance of seeing their conditions improve, the hospital found after an investigation.

The hospital said that six additional patients were given excessive doses of fentanyl but that it was not likely the cause of their deaths.

Thirty-five people died while under Husel’s care. He was charged with 25 counts of murder because prosecutors included only patients who died with fentanyl dosage levels of 500 micrograms and above, Ron O’Brien, the Franklin County prosecutor, said in June.

“Expert witnesses said dosages at that level could not support any legitimate medical purpose,” O’Brien said at the time.

Husel, who has pleaded not guilty, faces a possible prison sentence of 15 years to life for each murder charge.

Richard Blake, Husel’s lawyer, said last month that his client had tried to comfort dying people, not kill them.

This article originally appeared in The New York Times.