When Abdulahi Hasan Sharif was flagged as a potential terrorist threat two years ago, police in Alberta complained they were overwhelmed with Islamic State-inspired suspects. Now, as the 30-year-old Somali refugee appears in court accused of attempting to murder five people, questions remain about how he became radicalized and how the RCMP evaluated the potential threat he posed to the public.

Mr. Sharif is facing 11 charges, including five counts of attempted murder, five of dangerous driving causing bodily harm and one weapons offence. Although police have described the incident as a suspected terrorist act, terrorism charges have not been laid.

RCMP Superintendent Stacey Talbot told a news conference on Monday a terrorism investigation is continuing.

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Related: What we know so far about the suspected terrorist attack in Edmonton

Read more: Edmonton attack suspect facing terrorism charges was investigated by RCMP in 2015

"The complexities of a terrorism investigation are vast," she said. "We continue to collect and gather information related to this investigation … if additional charges are supported, they will be pursued at that time."

The investigation is being led by the RCMP's specialized Integrated National Security Enforcement Teams, or INSET(s).

Public Safety Minister Ralph Goodale and the RCMP have refused to give details of the 2015 investigation, with the RCMP saying only that they conducted a thorough probe based on a tip Mr. Sharif was "espousing extremist ideology," but found nothing to indicate he was a threat to public safety and no evidence to support charges or a peace bond, or even continue the investigation.

Amarnath Amarasingam, an academic co-directing a study of Western foreign fighters at the University of Waterloo, said Alberta generated about as many terrorism suspects as Quebec and Ontario in that period. And at that time, Edmonton Police Chief Rod Knecht said publicly his force was struggling to keep up with the number of terrorism suspects in Edmonton.

Chief Knecht told The Globe and Mail in an interview in 2015 that the common wisdom was that the terrorism threat was a problem in Toronto, Montreal or Vancouver.

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But he added: "I will absolutely tell you we are challenged for resourcing. … I'll go a little further, INSET is challenged for resources."

Saturday night's incident unfolded over several hours after a man drove a white Malibu through a roadblock and hit a police officer directing traffic outside a CFL football game, then stabbed the officer multiple times with a large knife. Police say the man fled police and later tried to run down pedestrians with a U-Haul, injuring four before he was arrested. Police have said an Islamic State flag was in his car.

Constable Mike Chernyk, who was hit by a car and stabbed repeatedly, emerged with remarkably few injuries, and was released from hospital early Sunday. Two of the pedestrians have also been released, and the two others remain in hospital, one in serious condition.

The CBC reported Mr. Sharif worked on a construction crew at one point, and quoted an unnamed former colleague saying Mr. Sharif was sympathetic to the Islamic State, prone to religious rants about "polytheists" and expressed "genocidal beliefs." The man said he reported Mr. Sharif to the RCMP, which resulted in the 2015 investigation.

Mr. Goodale has said Mr. Sharif arrived in Canada in 2012 and was granted refugee status, but few other personal details have emerged.

Conservative Pierre Paul-Hus questioned Mr. Goodale in the House of Commons on Monday, saying "Canadians need to know which information the RCMP had on this individual to undertake the investigation."

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On Monday, an unmarked police car was parked in front of the plain three-storey building listed as Mr. Sharif's address in court documents. Resident Grant Brunelle said police showed him a photo of Mr. Sharif, but he did not recognize him.

"It is pretty tragic what happened," he said. "It is very shocking."

Ahmed Abdulkadir, executive director of the Ogaden Somali Community of Alberta Residents, said he did not know Mr. Sharif, but is concerned his actions will affect Muslim and Somali communities in Edmonton.

"It's something that you have nothing to do with it, but at the same time, you have some kind of association with it," Mr. Abdulkadir said in an interview on Monday, in offices just a few blocks from where Constable Chernyk was hit and stabbed.

"We are Muslims, we are Somalis, we are Canadians – first and foremost – and we are Edmontonians. We are part of the fabric of this country."

At the Al Rashid Mosque – Canada's oldest mosque, built in 1938, and Edmonton's largest – outreach Imam Sadique Pathan said he is horrified by the weekend attack, but also concerned about backlash against the city's 100,000 Muslims.

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He said the community, government and law enforcement groups have been working together to identify radicalized individuals, but it is not easy.

"This is the other reality – we are coming to a time where extreme fringes and those voices are finding a place on the Internet," he said. "They are mobilizing, they are organizing."

With reports from Marty Klinkenberg in Edmonton and Justin Giovannetti and Carrie Tait in Toronto.