"People had very superficial relationships with him," said Stephane Pressault, who met Maguire four years ago during Friday prayers at the University of Ottawa.
Pleasantries were exchanged, but no deep ideas were shared, said Pressault, the national co-ordinator with outreach group Project Communitas.
"When you can't have intimate conversations with someone ... this young man was really quite isolated, no one really knew what he was thinking," Pressault recalled.
"It's not that he was a loner. But he didn't share his opinions on things. And he didn't have ... a best friend, or a clique, or a group of people that he always turned to.
"In retrospect, that's alarming."
Project Communitas is grappling with the phenomenon of Islamic radicalization as part of its mission to foster citizenship, dialogue and youth leadership.
"I think the common sign is really social isolation," Pressault said.
"How can we engage these individuals who are isolated, who are not in the mainstream and following the majority of the Muslims in Canada?"
Maguire's polished propaganda video, released Sunday, urged Muslims to launch indiscriminate attacks against Canadians, similar to those carried out in October in Ottawa and St-Jean-sur-Richelieu, Que.
Maguire — whose passport was apparently revoked after he left Canada — likely became "fed up" with Canadian society at some point, said Jocelyn Belanger, a psychology professor at the University of Quebec at Montreal who has studied radicalization around the world.
Belanger surmises Maguire could have been spurred to join radical Islamic militants overseas because he didn't fit in at home and felt insignificant — a typical motivation for extremists.
"The loss of significance deeply hurts," Belanger told the Senate committee on national security and defence.
One can regain prominence by building a successful career or becoming a role model, Belanger said, but such accomplishments take time.
"The highway to significance, if you wish, is fighting for radical ideology — which provides significance through a demonstration of power, harming victims and inducing fear in others."
This is why propaganda created by the al-Qaida splinter group known as the Islamic State of Iraq and the Levant, or ISIL, has been so effective, he added: "Their ideology dictates the actions required to become a hero, a martyr, a rock star."
The government has pointed to the latest video and the spectre of attacks by homegrown radicals as evidence of the need for additional legislative tools to protect Canadians.
Public Safety Minister Steven Blaney reiterated Monday that new anti-terrorism legislation is coming, but he offered no specifics or even a timeline.
The government should be "throwing money hand over fist" at the RCMP's fledgling program to counter violent extremism, University of Ottawa law professor Craig Forcese told the committee.
The problem of radicalization cannot be solved solely through prosecutions and penitentiaries, he warned.
Canadians must accept that efforts to discourage extremism will go on for years, said Jez Littlewood, who teaches at Carleton University's Norman Paterson School of International Affairs.
"It involves outreach to communities, it's going to involve a substantial element of trust between communities and authorities for it to work."
Pressault said it is disturbing to think someone can come to believe Islam means going to fight abroad or to wage war against Canadians.
"It's something that the whole community is thinking about," he said. "How do we engage these young people who may be prone to that?"
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