Reta Mays’ spree as a serial killer ended in July 2018, but only after she got away with murdering military veterans for a year.

On Tuesday in U.S. District Court in Clarksburg, West Virginia, Mays pleaded guilty to seven counts of murdering veterans who were patients at the Department of Veterans Affairs hospital in the same city. Mays, 46, also pleaded guilty to a count of assault with intent to murder.

Her pleas end months of uncertainty about the chain of suspicious deaths at the VA facility. While they were pursuing their probe, federal authorities refused to comment on it, other than to say the person of interest in their case was no longer employed at the hospital.

Though Mays pleaded guilty to only seven murder charges, it is possible she killed others. She began work as a nursing assistant at the facility in June 2015.

Plea documents in her case indicate the first murder to which she pleaded guilty occurred in July 2017. It was not until June 2018 that a doctor expressed concern about patients who had died under suspicious circumstances. We know now that Mays was injecting insulin into them when they did not require it — killing by sending the veterans into hypoglycemia.

How is it that no one noticed the suspicious deaths until nearly a year had passed? How is it that Mays had access to insulin, even though she was not authorized to administer any medicine? How is it that when Mays was hired, the VA did not even require nursing assistants to be certified or licensed?

Congress should demand answers from the VA. Otherwise, there will be no way of knowing what went wrong — and what the government is doing to keep it from happening to other men and women who served our country.