A former Canadian nurse pleaded guilty Thursday to killing eight elderly assisted-living residents who were in her care. In her confession, 49-year-old Elizabeth Tracey Mae Wettlaufer revealed to investigators that she thought God wanted her to kill them. She also told them that some of the victims, she simply killed out of spite because they were “mean.”

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Wettlaufer told investigators that she killed her patients, all of which were between the ages of 75 to 96, with a lethal dose of insulin. The murders took place between 2007 and 2014,

Wettlaufer said she was angry about the way her life and career turned out. That anger apparently came to a boiling point and “she felt the urge to kill,” according to The Associated Press.

She told the court that she knew right from wrong and was not under the influence of any drug or alcohol.

Her reign of terror came to an end after law enforcement received a tip that Wettlaufer may have been killing the patients under her care. Investigators believe Wettlaufer’s decision to begin killing her patients was linked to her frustration over finding steady employment and her separation from her husband.

“I just had a sense after my marriage broke up that God was going to use me for something,” Wettlaufer said in a videotaped confession to the police. “After a while, I started to really wonder, after some of the murders, if it was God or if it was the Devil fooling me.”

Wettlaufer’s mother, Hazel Parker, told CNN that her daughter has a bipolar disorder and could have been off her medication. The former nurse told a local priest of her horrendous acts, but nothing ever came of it.

She is heard in the video stating, “Maybe they didn’t believe me,” she claimed. “I don’t know. Maybe they just thought I was doing something that the patient wanted.”

The Registered Nurses Association of Ontario made a statement to The New York Times: “We need to get to the bottom of what happened, how it happened and what we can learn from an organizational, regulatory and system perspective to ensure nothing like this ever happens again.”

Wettlaufer, if convicted, could face life in prison. She is scheduled to be sentenced towards the end of June. Sadly, this is one of the worst serial killer cases in Canada’s history.