Updated at 12:40 p.m. ET
Federal prosecutors have charged a former nursing assistant at a medical center for veterans in West Virginia with seven counts of second-degree murder.
Reta Mays, who worked at the Louis A. Johnson Veterans Affairs Medical Center in Clarksburg, is accused of killing seven patients by injecting them with insulin. She is also charged with assault with intent to commit murder regarding an eighth patient.
Mays worked the night shift from 2015 to 2018 at the medical center, in a ward that housed many patients who had diabetes, according to the charging documents.
In 2018, prosecutors say a doctor reported "a concern about the deaths of patients who had suffered unexplained hypoglycemic episodes," a condition linked to a surplus of insulin in the body. Hypoglycemia means that the patient has low blood sugar and, in severe cases, can lead to coma and death.
Some of these episodes involved patients who were not diabetic.
The doctor's report prompted an investigation and culminated in the federal charges filed Monday in U.S. District Court in West Virginia.
According to the prosecutors, a nursing assistant was not required to have a license or certification to work at this VA medical center.
The victims named in the charging documents are Robert Edge Sr., Robert Kozul, Archie Edgell, George Shaw, Felix McDermott, Raymond Golden and another patient listed only by the initials W.A.H. All of them died between July 2017 and June 2018.
The eighth person, whom Meta is accused of assaulting in June 2018, is identified only as R.R.P.
McDermott, a Vietnam veteran, had been admitted to the hospital because of aspiration pneumonia before he died, as West Virginia Public Broadcasting's Dave Mistich reported last year.
"We thought he had died of natural causes, only to find out in late August , when the FBI showed up at my house, that he didn't," his daughter, Melanie Proctor, told Mistich. "And we have been waiting for answers ever since."
A family attorney told NPR's Vanessa Romo last year that McDermott died because of "one massive insulin injection."
Mays is scheduled to appear in federal court on Tuesday at 2 p.m. ET.