WASHINGTON – Authorities are investigating a string of about 10 suspicious deaths of patients, including one ruled a homicide, at a Veterans Affairs hospital in West Virginia out of concern they were targeted, according to three people familiar with the probe.

In October, the body of Felix Kirk McDermott, an 82-year-old Army veteran who died last year at a VA hospital in Clarksburg, West Virginia, was exhumed and brought to Dover Air Force Base in Delaware.

A federal medical examiner conducted an autopsy and concluded that McDermott’s sudden death on April 9, 2018, was caused by an injection of insulin into his abdomen – which can kill someone who is not diabetic.

There was no order for the injection in McDermott’s hospital records, and he had no history of diabetes or insulin use to control his blood sugar levels, according to the autopsy report.

"It’s just not right," his daughter Melanie Proctor told USA TODAY. "I thought my dad was safe there."

Proctor, whose father had dementia, and her lawyer said investigators with the VA’s Office of Inspector General told them his death is one of about 10 they are reviewing, a figure confirmed by a person briefed on the federal investigation who spoke on condition of anonymity.

Proctor said they told her the other veterans were "all about in the same shape," and they all received suspicious doses of insulin.

Authorities are investigating a "person of interest" in the case, according to the office of U.S. Sen. Joe Manchin, D-West Virginia, and a claim filed with the VA by McDermott’s family.

In response to inquiries from USA TODAY, a spokesman for the VA in Clarksburg said the matter doesn’t involve any current employees.

The VA notified the inspector general’s office of "serious allegations” of potential misconduct at Louis A. Johnson VA Medical Center discovered last year, spokesman Wesley Walls said by email. The hospital has since put "safeguards in place to ensure the safety of each and every one of our patients."

The Veterans Administration "is cooperating fully with the inspector general’s ongoing investigation, and for additional questions we refer you to them," Walls said.

VA Inspector General Michael Missal issued a statement Tuesday confirming his office is working with federal law enforcement “to investigate allegations of potential wrongdoing resulting in patient deaths” at the VA hospital in Clarksburg.

“At this time, we cannot comment further on those activities,” he said.

The FBI referred inquiries to the U.S. Attorney’s Office in West Virginia. Stacy Bishop, a spokeswoman for U.S. Attorney Bill Powell, declined to address the matter. “As a matter of general policy, we will neither confirm nor deny the existence of any ongoing investigation,” Bishop said.

The suggestion of a string of deaths, including McDermott’s, was reported by The Exponent Telegram in Clarksburg, West Virginia, on Friday.

'No longer in contact' with veterans

The story drew the attention of Manchin, who spoke with VA officials Monday. They assured him the "person of interest" in the deaths is "no longer in any contact with veterans at the VA facility," Manchin said in a statement.

"As a member of the Senate Veterans’ Affairs Committee I will do everything in my power to investigate these accusations and get to the bottom of what happened," he said. "These families and loved ones deserve answers as soon as possible and I will make sure they get them."

Proctor’s lawyer, Tony O’Dell of the law firm Tiano O’Dell in Charleston, West Virginia, filed an administrative wrongful death claim with the VA last week, a preliminary step before filing a lawsuit. The claim seeks $6 million and alleges VA medical center employees "knew or should have known that its patients were being wrongfully injected with insulin."

O’Dell told USA TODAY that investigators told Proctor that her father’s death was among the last of the 10.

"It should never have gotten to Mr. McDermott," he said.

Proctor told USA TODAY on Monday that when her father died in April 2018, hospital officials gave her the impression that his death had been unavoidable – something that could happen to anyone in his condition.

Her father had suffered a stroke a few years earlier and had "full-blown dementia," Proctor said. He also suffered from heart disease, hypertension and chronic obstructive pulmonary disease. Three days before his death, he was admitted to the hospital with pneumonia after he aspirated food into his lungs.

It wasn’t until FBI agents came to her home a few months after her father’s death, Proctor said, that she learned the circumstances were suspicious. She gave investigators with the VA’s Office of Inspector General, whose office is the internal investigations branch within the department,permission to exhume his body in October.

Although McDermott had several long-term health problems, his condition was improving after a couple days in the hospital, according to the autopsy report.

The autopsy revealed an insulin injection site on McDermott’s left side, which would explain why his blood sugar level suddenly dropped dangerously low on April 9, 2018.

Diabetics can take insulin to control their blood sugar levels. But if a person without diabetes receives an insulin injection, it can lower their blood sugar too much and cause death, according to a National Institutes of Health study.

'Manner of death is homicide'

McDermott died several hours after his blood sugar dropped, according to the autopsy report.

"Based on the investigative and autopsy findings, the manner of death is homicide," the medical examiner wrote in his report.

McDermott’s death certificate now says his death was a homicide, the result of a non-diabetic patient being injected with insulin "by an assailant."

His daughter said the discovery left her feeling "hurt and betrayed."

"I expected him to be taken care of, especially somebody with dementia that can’t talk for themselves," she said.

Before he was admitted to the hospital, McDermott resided at the VA nursing home on the campus of the VA medical center. Proctor said she and other family members visited regularly and brought him chocolate, which he enjoyed.

McDermott retired from the Army as a sergeant major after 20 years of active duty, including a tour in Vietnam, Proctor said.

She said her father had a "wicked" sense of humor and was ready to help neighbors and strangers alike. "I don't care if he was mad at you or not, he'd do whatever you needed him for."

Proctor said she hopes her legal action – and speaking out publicly – triggers improvements at the VA.

"I don’t know what happened to set this chain off, so I can’t even say what needs to be improved upon at this point," she said. But she knows one thing: "It shouldn’t happen to any other families."

Kevin Johnson contributed reporting.

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