An Ohio University graduate was charged Wednesday on 25 counts of murder in the case of a Columbus Hospital.

William Husel, a former doctor at Mount Carmel and 2008 graduate from OU with a doctorate of osteopathic medicine, turned himself in to Columbus police Wednesday morning after a criminal investigation concluded he purposefully caused the deaths of patients by ordering excessive painkiller doses for four years, according to a Columbus Dispatch article.

The charges against Husel, 43, of Liberty Township, say the 25 victims were given at least 500 micrograms of fentanyl, which Franklin County Prosecutor Ron O’Brien said was potentially fatal, according to a Columbus Dispatch article.

Mount Carmel Health System said Husel ordered excessive doses of painkillers for 35 patients, but they do not believe six of those patients died because of the drugs.

Some patients received 1,000 micrograms, and two patients received 2,000 micrograms, according to a Columbus Dispatch article.

Fentanyl is an opioid that was developed for pain management for cancer treatments. It is 80-100 times stronger than morphine and 50 times more potent than heroin, according to the United States Drug Enforcement Administration.