Montreal police are trying to connect the dots between an attack on a patient in a city hospital and two earlier deaths at the same facility that have since been ruled as slayings.

Two unidentified male patients at Notre-Dame Hospital’s psychiatric unit were suffocated on June 16 and June 21.

Staff initially believed the two men, aged 69 and 77, died of natural causes. But after a third patient was attacked in the same unit on June 22, the hospital and police investigated further.

Autopsies showed the two deaths were actually murders.

Thirty-one-year-old Idelson Guerrier of Joliette, Que., who is a patient at Notre-Dame Hospital, has been charged with assault with a weapon and break-and-enter in connection with the attack on a 71-year-old female patient.

Guerrier will undergo a psychological evaluation, after which police said they may question him about the deaths of the other two patients.

Police have said that, at this point, Guerrier is not considered a suspect in the two murders.

"Police are confirming there is no suspect at this time," CTV Montreal’s Cindy Sherwin reported Thursday. "They've made no official arrests, there are no charges at this moment being laid, they're still investigating, are still connecting the dots related to the two deaths that they now believe were two murders."

The public wasn’t notified of the murders until 11 days after the first death.

Hospital officials said they delayed making the deaths public because families of the victims were being contacted.

They insist the murders were “isolated incidents” and that Notre-Dame Hospital has a good security system, although the hospital will conduct a review to see if any changes are necessary.

Patients on the psych ward can move around freely because it’s “not a prison,” hospital spokeswoman Lucie Dufresne said.

Dr. Paul Lesperance, the chief of psychiatry at the University of Montreal hospital network, which includes Notre-Dame, told reporters that a risk assessment was done on Guerrier before he was admitted to hospital.

Sherwin reported that Guerrier was known to police, but Lesperance said privacy laws can make it difficult for hospitals to access information about patients’ run-ins with the law.

“We try to get this information. We don’t usually get it on the first day,” he said.

The union representing health-care workers at Notre-Dame Hospital said it warned management last year about the negative impact of staffing cuts to the psychiatric department.

"We're wondering whether there's a link between these cuts and these events," union president Guy Brochu said Thursday.

Dufresne said the unit was adequately staffed at the time of the murders.

With a report from CTV Montreal’s Cindy Sherwin and files from The Canadian Press