CHARLESTON, W.VA. -- A former nursing assistant who killed seven elderly veterans with fatal injections of insulin at a West Virginia hospital was sentenced to life in prison on Tuesday by a federal judge who called her “the monster that no one sees coming.”

Reta Mays has a history of mental health issues, and offered no explanation Tuesday for why she killed the men. But U.S. District Judge Thomas Kleeh told her “you knew what you were doing” before sentencing her to seven consecutive life terms, a punishment that means she'll likely die in prison.

Mays, 46, pleaded guilty last year in federal court to seven counts of second-degree murder for intentionally injecting the men with unprescribed insulin at the Louis A. Johnson VA Medical Center in Clarksburg.

While the deaths accumulated during her overnight shifts at the hospital in 2017 and 2018, Mays conducted internet searches on female serial killers and watched the Netflix series “Nurses Who Kill,” Kleeh said. He also said she repeatedly denied her involvement, telling investigators three times that she had no knowledge of the crimes.

“Several times your counsels made the point that you shouldn't be considered a monster,” Kleeh told Mays. “Respectfully, I disagree with that. You are the worst kind. You're the monster that no one sees coming.”

Mays cried and apologized in addressing the court briefly before learning her sentence.

“I know that there's no words that I can say that would alter the families' pain and comfort,” she said. “I don't ask for forgiveness because I don't think I could forgive anyone for doing what I did.”

Hospital officials reported the deaths to the VA inspector general and fired Mays after evidence pointed to her.

An interview with Mays after her guilty plea was included in a lengthy report released after Tuesday's sentencing by the Department of Veterans Affairs' Office of Inspector General detailing deficiencies at the hospital.

In it, she said she administered insulin to patients she believed were suffering so that they could pass “gently.” She said she also had great stress and chaos in her personal and professional life, and that her actions gave her a sense of control.

But Assistant U.S. Attorney Jarod Douglas called her actions “predatory and planned, not reactionary.”

“These men were not in need of mercy by the defendant,” Douglas said. “In the end it wasn't the defendant's call to make.”

Mays' attorney, Jay McCamic, described her long history of depression, anxiety, mental health and other medical issues, including a trip to the emergency room when a patient knocked her unconscious with a punch to the face in May 2016.

“Many, many people ask why, why did Reta do this?” McCamic said. “Most people want to have a nice, linear story applied to the conspiracy, a unified motive of why someone would set upon the idea of taking the life of others and go forth with that idea. Unfortunately, why is not a question that can be answered here. Reta doesn't know why. Her family doesn't know why.”

Mays, of Reynoldsville, had served in the Army National Guard in a noncombat position in Iraq and Afghanistan.

Her duties at the hospital included measuring patients' vital signs and blood glucose levels. VA nursing assistants are not qualified or authorized to administer medication, including insulin, prosecutors said. The hospital's nursing assistants also were not required to have a certificate or license as a condition of continuing employment.

Then-U.S. Attorney Bill Powell said there were about 20 suspicious deaths at the medical center during the time Mays worked there, but charges were only brought in cases where the government thought it had sufficient evidence.

The second-degree murder charges involved the deaths of Army veterans Robert Lee Kozul Sr., 89, Archie D. Edgell, 84, Felix Kirk McDermott, 82, and William Holloway, 96; Navy veteran Robert Edge Sr., 82; Air Force veteran George Nelson Shaw Sr., 81; and Army and Air Force veteran Raymond Golden, 88.

She also was sentenced to an additional 20 years for assault with intent to commit murder involving the death of Navy veteran Russell R. Posey Sr., 92.

Separately, the federal government has agreed to the settlement of numerous lawsuits filed by veterans' families alleging a widespread system of failures at the hospital.

The VA is responsible for 9 million military veterans. The agency's former director was fired in 2018 in the wake of a bruising ethics scandal and a mounting rebellion within the agency. Robert Wilkie took over as Veterans Affairs secretary in July 2018.