A former nurse has been charged with murdering eight care-home residents in southwestern Ontario over seven years, a string of deaths that would make her among the worst serial killers in Canadian history.

Elizabeth Wettlaufer, 49, of Woodstock, Ont., faces eight counts of first-degree murder, charges that have shaken the community and shocked families of the dead. Ms. Wettlaufer was taken into custody after a brief court appearance in the small city between Hamilton and London on Tuesday.

The deaths took place between 2007 and 2014, seven of them at a home in Woodstock and one at a home in London. Police say the alleged victims were given a fatal dose of a drug.

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Although officers would not say what kind of drug, or how it was administered, a peace bond placed on Ms. Wettlaufer after police began investigating in late September reveals she was prohibited from possessing insulin, or any other medication unless prescribed for her personal use.

The alleged victims have been identified as James Silcox, 84, Maurice Granat, 84, Gladys Millard, 87, Helen Matheson, 95, Mary Zurawinski, 96, Helen Young, 90, Maureen Pickering, 78, and Arpad Horvath, 75.

"We're living my father's death right now," said Daniel Silcox, son of James Silcox. "It's horrific."

Mr. Horvath lived at Meadow Park Long Term Care in London. The other seven alleged victims lived at the Caressant Care home in Woodstock. Ms. Wettlaufer worked at both facilities.

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Families in the region and across the country say they are angry, and in mourning all over again.

Maurice Granat's daughter, Connie Dreyer, 68, said she did not want to speak about the ordeal, as she wiped tears from her eyes. Mr. Granat's granddaughter, who declined to give her name, said she is angry.

Ms. Wettlaufer's lawyers – Michael Smith, a Woodstock-based defence counsel, and Brad Burgess, an associate at the high-powered Toronto firm Lockyer Campbell Posner – declined to comment.

The Globe and Mail has learned that one week after police received a detailed tip that a nurse had been involved in eight killings, Ms. Wettlaufer agreed to the conditions of the peace bond – a protective order sought by law enforcement when there are reasonable grounds to believe a person appears likely to commit a serious personal injury offence.

According to court documents dated Oct. 6, Ms. Wettlaufer was expected to obey a 7 p.m. curfew, refrain from providing services as a care giver, stay out of nursing homes and not consume alcohol, among other conditions.

The College of Nurses of Ontario also noted that Ms. Wettlaufer, who had been a nurse since 1995, resigned her licence on Sept. 30, one day after police launched their investigation. The college would not comment on the circumstances of her resignation.

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News of the allegations prompted mourning and debate in Ontario's legislature on Tuesday, with opposition parties asking the Liberal government how this could have happened in provincially regulated facilities.

Teresa Armstrong, a New Democrat who represents the London area, asked Premier Kathleen Wynne how such things could happen under the oversight of the Ministry of Health and Long-Term Care.

"How do [alleged] murders go undetected for nearly 10 years inside any long-term-care home in Ontario?" Ms. Armstrong said.

Ms. Wynne, along with her health minister and attorney-general, refused to answer direct questions on the matter, citing the police investigation.

"This is an extremely distressing and tragic, tragic thing for all of the families involved," she said.

Nursing homes in the province must report patient deaths to the Office of the Chief Coroner for Ontario. But the coroner's office does not investigate all deaths in long-term care, said Cheryl Mahyr, a spokeswoman for the Office of the Chief Coroner. The office launches investigations under certain circumstances only, such as when a nursing-home death is "sudden and unexpected." Autopsies are performed in about one-third of all investigations, she added.

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The coroner's office used to conduct mandatory investigations of every 10th death at a nursing home, but dropped that practice in 2013, in part because the Ministry of Health and Long-Term Care fortified its oversight of nursing homes a few years earlier.

Since the coroner's office changed its policy in 2013, it has probed far fewer nursing-home deaths. The office conducted 2,027 investigations in long-term-care facilities in 2013. The number plunged to 890 in 2014 and 884 in 2015. (Ms. Mahyr would not say if a coroner investigated any of the eight deaths in this case, citing the police investigation.)

"I think we need to do more spot checking to see what's happening in those homes, [by] drawing blood or doing full autopsies," said Jane Meadus, a lawyer with the Advocacy Centre for the Elderly.

Nursing homes in Ontario are also required to report critical incidents to the ministry. An unexpected or sudden death counts as a critical incident that has to be communicated to the ministry immediately. None of the publicly available critical-incident inspection reports for Caressant Care Woodstock and Meadow Park in London dating back to 2010 mentioned sudden or unexpected deaths.

Medications, especially narcotics, are supposed to be strictly controlled inside nursing homes, according to Candace Chartier, the chief executive officer of the Ontario Long Term Care Association, which represents nursing homes across the province, including the two homes where the murders are alleged to have taken place.

"Double signatures are required for every part of giving a narcotic – giving it, wasting it, discontinuing it," Ms. Chartier said, adding that only registered nurses and registered practical nurses are allowed to sign off on narcotics. As a registered nurse, Ms. Wettlaufer could have had access to narcotics and other pharmaceuticals.

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A nurse who worked at Caressant with Ms. Wettlaufer for several years said the accused often worked the overnight shift in one of the home's two sections. On those occasions, the woman said, Ms. Wettlaufer would have had sole access to three locked medical carts containing a week's worth of medication for up to 99 residents.

The woman, who asked not to be named for privacy reasons, said a nurse must sign a document each time he or she administers a medication to a client. She also said that when one shift ends and another begins, nurses conduct a narcotics count to ensure everything is "present and accounted for."

Whenever a nursing home makes a new hire, the nurse is required by law to complete a criminal background check within six months of starting work. If a nurse is later charged with or convicted of a crime, the nurse is supposed to share that information with the employer. The College of Nurses of Ontario, the self-regulatory body that governs the nursing profession, recorded no criminal charges or disciplinary action against Ms. Wettlaufer before Tuesday.

Glen Smith, a son-in-law of James Silcox, said that learning from investigators about three weeks ago that Mr. Silcox was part of a homicide investigation was "shocking."

The terrible new perspective on Mr. Silcox's death has forced the family to reassess a sad chapter in their lives that they believed was closed, he said.

With reports from Kathryn Blaze Baum, Colin Freeze, Patrick White, Tu Thanh Ha, Kelly Grant, Adrian Morrow and The Canadian Press

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Editor's note: An earlier version of this story incorrectly said that police started the case based on a tip received Sept. 8. In fact they received the tip on Sept. 29.