News that French-Canadian student Alexandre Bissonnette faces six counts of first-degree murder and five of attempted murder has come as a shock to many who knew him at work, university and at home.
Most people talking about him to Canadian media describe him as introverted, shy and unassuming.
Only occasionally do glimpses of the man who is alleged to be one of Quebec's worst mass murderers shine through.
Mr Bissonnette's Facebook page, which has now been deleted, said that he lived in a suburb close to Quebec City and was a naval cadet as a child.
It carried pictures of him not dissimilar to any other postings by a man of his age and background - in his case attending what appear to be family gatherings and a selfie in which he says he is "driving to my camping ground".
Another post in November featured a video of Torngat Mountains National Park in Newfoundland with the caption: "I will visit this place one day!"
Mr Bissonnette, 27, rented a flat with his twin brother near the Quebec Islamic Cultural Centre, where Sunday's shooting took place, CBC News Montreal reported.
He studied political science and anthropology at Laval University, whose campus is also close to the mosque. He was known to be keen on video games, a competent musician and active at the university's chess club.
"He gave the impression of being a very good person," Prof Jean Sevigny told thestar.com , while a university classmate told the website that Mr Bissonnette did not seem like a violent person.
"He was timid, [an] introvert. Awkward a bit," the classmate is quoted as saying.
But the alleged darker side to his character was believed by some to be never far away. Francois Deschamps, an official with an advocacy group, Welcome to Refugees, said the suspect was known for his far-right views.
Mr Bissonnette was "unfortunately known to many activists in Quebec for taking nationalist, pro-(French far-right politician Marine) Le Pen and anti-feminist positions at Laval University and on social media," Mr Deschamps posted on the organisation's Facebook page.
A neighbour is quoted as saying that he was "very solitary", "withdrawn" and "very antisocial".
Fellow student Vincent Boissoneault told the Globe and Mail that while Mr Bissonnette's "online profile and school friendships" did little initially to reveal his extremist beliefs, more recently they became much more apparent.
That was especially the case when Marine Le Pen visited Quebec City, prompting Mr Bissonnette to express much more extreme online views in support of her.
"I wrote him off as a xenophobe," Mr Boissoneault said. "I didn't even think of him as totally racist, but he was enthralled by a borderline racist nationalist movement... [But] it never occurred to me he might be violent."
Mr Deschamps told The Globe and Mail: "He was someone who made frequent extreme comments in social media denigrating refugees and feminism. It wasn't outright hate, rather part of this new nationalist conservative identity movement that is more intolerant than hateful."
Both Mr Deschamps and Mr Boissoneault describe how the previously reticent and subdued student began expressing strong anti-immigration opinions which were especially directed towards Muslim refugees.