"We're wondering whether there's a link between these cuts and these events," union president Guy Brochu said Thursday. When pressed, he could not immediately provide specific numbers on the staffing cutbacks.
"Could we have avoided (the deaths)?"
Two male patients - aged 69 and 77 years old - were killed by asphyxiation in the hospital's psychiatric ward on June 16 and June 21.
One day after the second death, a 71-year-old female patient was allegedly assaulted in the ward; she survived the alleged attack.
Police were called in, and a 31-year-old psychiatric patient was arrested.
The man, Idelson Guerrier of Joliette, Que., has been formally charged with assault with a weapon and break and enter with criminal intent.
Police investigators are now trying to determine whether the suspect is connected to the deaths. A department spokeswoman said detectives have already questioned the man and may want to interrogate him again after he undergoes a psychiatric evaluation.
Initially, hospital staff did not suspect foul play in either of the deaths. Officials said both victims suffered from medical problems as well as psychological ones.
"These deaths seemed to be natural," said hospital spokeswoman Lucie Dufresne.
The institution does not routinely call for autopsies when someone dies, but the attack changed everything for these two cases.
When police were called in, staff told them about the recent patient deaths.
It was only then that autopsies were carried out on the bodies and tests discovered that both men died by asphyxiation, Dufresne said.
The head of a patients' rights group said Thursday he was troubled by the fact the deaths were initially blamed on natural causes.
"It sends shivers up the spine," said Paul Brunet, president of the Conseil pour la protection des malades.
He said patients have a right to feel secure in a hospital and asked how an individual who was allegedly "that violent" found his way into the institution.
The hospital kept the deaths and the assault quiet for days.
Dufresne said officials needed the time to alert families of the victims, and of the other patients in the psychiatric ward, before going public.
The goal was to keep people from wondering about their loved ones.
She said the relatives of the victims and each of the approximately 70 patients in the unit were contacted before the hospital released the information late Wednesday.
She also sought to downplay concerns about security - and pointed out that the hospital is not a detention centre for people with violent behaviour.
Psychiatric patients have freedom to circulate, which Dufresne said is common in a hospital setting.
"Psychiatry in hospital is not a prison," she said.
"So patients have a certain liberty... It's a therapeutic place where people can recover."
Dr. Paul Lesperance, chief of Notre-Dame's psychiatric unit, said the suspect had been under the watch of his ward's intensive-care specialists, a standard procedure for patients previously unknown to the team.
Hospital officials insist that, according to provincial norms, a sufficient number of employees were on duty when the deaths and the attack occurred.
But they say they have still launched an internal evaluation to determine whether improvements are needed.
The union president wonders whether the hospital will make enough changes.
On Thursday, one reporter took the elevator to the psychiatry ward and talked to several people without any problems. A security guard eventually caught up with her and asked her to leave.
Brochu said management answered the concerns last year by arguing that staffing levels at Notre-Dame fell within the guidelines and that other hospitals had comparable numbers of employees.
"If it's like this everywhere, could the same event happen in other hospitals?" said Brochu, who added that he's fielded union members' complaints that the psychiatric ward is understaffed.
"We can't just say that everything was done within the golden rule and accept that it continue like this.
"There has been a super-maddening event that was committed."
- with a file from Melanie Marquis
Note to readers: This is a corrected story. Earlier versions wrongly said there was a charge of attempted murder, and listed the second death as having occurred on June 22.