Investigations are underway into allegations that a doctor working for an Ohio hospital system ordered inappropriately high doses of pain medication to dozens of patients, leading to the deaths of at least 28 people at two hospitals. A review of events so far based on information provided by Mount Carmel Hospital System, details in lawsuits and accounts from patients' family members:

Oct. 25: Columbus-based Mount Carmel receives formal report related to care provided by Dr. William Husel.

Nov. 19: Mount Carmel receives second formal report related to Husel's care and broadens an internal investigation.

Nov. 21: Mount Carmel receives a third report and prohibits Husel from providing patient care.

Dec. 5: Mount Carmel fires Husel, notifies the State Medical Board of Ohio and meets with Franklin County Prosecutor Ron O'Brien. Two days later, the hospital notifies the Ohio Boards of Pharmacy & Nursing.

Dec. 11: Mount Carmel begins training staff on changes in procedures and on existing and updated policies.

Dec. 27: Mount Carmel first contacts families of patients affected by Husel's actions to notify them and apologize.

Jan. 14: The first lawsuit is filed over the deaths, against the health system, a pharmacist, a nurse, and Husel, alleging a "grossly excessive" dosage of the powerful painkiller fentanyl was ordered to hasten the death of 79-year-old Janet Kavanaugh in December 2017.

The same day, allegations against Husel become public as the hospital system releases a statement revealing the deaths of 27 patients who received doses of pain medication that were potentially fatal. The hospital's President and CEO Ed Lamb apologizes and says they are investigating how it happened. In an internal video released to employees the same day, Lamb said Husel's orders were carried out by employees who "made poor decisions" and ignored existing safeguards.

Jan. 16: In the first public comments from a family member, David Austin, of Columbus, says he felt "like somebody kicked me in the chest" when he was told of the alleged circumstances of the death of his wife of 36 years, Bonnie Austin, in September. The same day, Mount Carmel says it identified a 28th patient. Attorneys for Hustel issue their first "no comment."

Jan. 17: The widow of a man treated by Husel says news of the circumstances of her husband's death left her shocked that such a scenario could happen despite procedural and technological safeguards. Christine Allison, of Columbus, says "the system failed tremendously" in the case of her 44-year-old husband, Troy.

Jan. 19: The Ohio Department of Health confirms its investigation of Husel on behalf of the U.S. Centers for Medicare and Medicaid Services.

Jan. 24: Mount Carmel acknowledges that Husel kept working for four weeks after concern was raised last fall. It also says it is now investigating whether some patients got excessive doses while they might still have had the opportunity to improve with treatment. The hospital raises the total number of patients receiving excessive doses of pain medication to 34.

Jan. 25: State Medical Board suspends Husel's license, says doctor invoked his right against self-incrimination when he met with representatives this week and was questioned. Two additional lawsuits filed, over the deaths of 69-year-old Joanne Bellisari in May 2015 and 80-year-old Jim Allen in May 2018, bringing the total to six lawsuits as of Friday.

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Associated Press writers Kantele Franko in Columbus and John Seewer in Toledo contributed to this report.