A top-level federal memo warning of a potential "violent act of terrorism in Canada" was distributed by the prime minister's staff five days before last month's attack on Parliament Hill, according to a copy obtained by CBC News.

The memo was circulated on the evening of Friday, Oct. 17 — three days before the Oct. 20 hit-and-run attack in St-Jean-sur-Richelieu, Que., by Martin Couture-Rouleau and five days before the Oct. 22 shooting in Ottawa by Michael Zehaf-Bibeau.

The alert directed security staff to ensure extra vigilance and strict compliance with security protocols. That included the updating of communications lines and emergency numbers to "ensure readiness in the case of an incident."

It is not clear what, if any, action was taken as a result of the federal alert. Security experts have cited a lack of vigilance on Parliament Hill when Zehaf-Bibeau was able to enter the Centre Block and fire his hunting rifle just steps away from the prime minister, who was meeting with his caucus nearby.

"They had enough warning that there should have been some security protocols put in place," said Garry Clement, a former RCMP superintendent who is now a security consultant.

"One of the things I thought they would have done is upgrade the security on Parliament Hill."

The alert was sent to security officers for all federal departments and agencies across Canada. Even so, counter-terrorism experts like Steve Day, a former commander of Canada's special forces, see little evidence of tightened security.

Pointing to the surveillance video from Zehaf-Bibeau's arrival on Parliament Hill, Day said last week, "If there would have been a police officer at those bollards when the shooter first departs his car, we've got a different scenario."

As it was, Day said, RCMP officers on the scene seemed to be in the dark, even after Zehaf-Bibeau hijacked a car at gunpoint and headed for the Centre Block.

"When you look at the RCMP cruiser outside Parliament Hill," Day said, "it doesn't move until the other cruiser passes it. It tells me he's not aware of an approaching threat."

'Act of terrorism could occur'

The warning from the Privy Council Office bears the all-caps heading, "HEIGHTENED STATE OF ALERTNESS," and is signed by Iwan Chan, acting executive director of security operations in the security and intelligence secretariat of the Privy Council Office — the prime minister's department.

It tells federal DSOs (departmental security officers) that a new report from the Integrated Threat Assessment Centre, known as ITAC, indicated "a violent act of terrorism could occur in Canada — although there is no information indicating that an attack is imminent."

Michael Zehaf-Bibeau is shown carrying a gun while running toward Parliament Hill in Ottawa on Oct. 22, in an image taken from video surveillance. Security chiefs in federal departments were warned five days earlier to be extra vigilant because 'a violent act of terrorism could occur.' (RCMP/Canadian Press)

While Chan's warning was circulated to the DSOs on Friday night, it is unclear whether it was forwarded to their front-line staff until late the following Monday, after the hit-and-run in Quebec. Some staff only saw it after 5 p.m. on Monday, three days after the PCO sent it out.

The e-mails forwarding the memo say the threat level across Canada had been raised from "low" to "medium." It also says the alert, while not classified, should not be passed on to the public or to the media. Rather, it was to be distributed on a "need-to-know" basis.

Whether that enabled officers in the field to see it is uncertain. Security experts point to the fact that, on the following Wednesday, Zehaf-Bibeau was able to shoot Cpl. Nathan Cirillo at the National War Memorial and to run unchallenged onto Parliament Hill with a hunting rifle. He then hijacked a ministerial car and drove past two RCMP cruisers, who did not interfere until after he passed. Finally, he was able to enter the Centre Block, where no-one had alerted security guards to lock the door.

He might have been stopped sooner if the PCO alert had been taken more seriously, said Clement, who oversaw Parliament Hill operations during his time in the RCMP.

"This is a classic case of, well, it's not happened, it probably won't happen, and the proper amount of resources and thought did not go into this."

Specific directions to tighten security

The Oct. 17 PCO warning gave specific directions to ensure that all security routines would be strictly observed. These include:

"ID cards clearly displayed at all time, access points controlled, visitor sign-in and escort procedures followed, building emergency response plans and business continuity plans up to date and ready to be activated."

"Encourage staff to remain vigilant and to report any suspicious activity, vehicles and/or persons around the perimeter of their facilities or within them."

"Ensure adequate monitoring, e.g. visual surveillance of all facilities, regular patrols, IT systems monitored, heightened situational awareness."

"Validate communications and notification protocols, e.g. internal communications to staff, emergency phone line, emergency notification system."

"For DSOs with responsibilities for the security of ministers, ministers of state or parliamentary secretaries, remain engaged with the RCMP to make any necessary adjustments to their security arrangements."

Threat level raised

The raising of the threat level to medium on Oct. 17 was not routine — it was the first time that happened in more than four years, since August 2010. In raising it, ITAC reported that "intelligence indicates that an individual or group within Canada or abroad has the intent and capability to commit an act of terrorism. ITAC assesses that a violent act of terrorism could occur."

Even so, the PCO memo highlighting the ITAC assessment urged security officers not to discuss the matter publicly. According to Garry Clement, a complacent attitude may have led many officers to shrug it off.

"The unfortunate part is, I think complacency has gone into the Canadian mosaic, amongst the authorities, and they stepped up security a little bit," Clement said.

"But the reality of it is, I don't think there was enough sensitivity and enough objectivity placed on this correspondence."

The PCO memo tells the security officers that, "At this time the Government of Canada does not publicly discuss the threat level. Communications on this matter will be reactive and led by Public Safety Canada."

Neither the minister of public safety, Steven Blaney, nor his officials would say what action, if any, was taken in response to the Oct. 17 alert.

"I don't comment on operational matters," Blaney told CBC News, adding, "the security of the hill is the responsibility of the Speaker of the House."

A spokesperson for the RCMP also declined to say whether the force took any action in response to the memo.