Shelley Brennan, 52, lives two doors from the home where Martin Couture-Rouleau grew up on a suburban street in Saint-Jean-sur-Richelieu, just south of Montreal.
Brennan said reports he had become radicalized were "news to her," but acknowledged she had seen a definite change in him.
"I just noticed recently that there was a new man in the neighbourhood and I thought he was Muslim," she said. "I just found out last night it was Martin, so I was totally shocked. That's how much he had changed.
"He was wearing a tunic, he had something on his head, he had a beard, his hair colour had changed.
"That's not the boy I remember."
Late on Tuesday, law enforcement formally identified Couture-Rouleau as the man shot dead by police after Monday's hit-and-run in the parking lot of a Saint-Jean-sur-Richelieu shopping centre.
Police confirmed they had been in contact with Couture-Rouleau and his relatives, who had detected subtle changes in the young man's behaviour and had sought help for him.
RCMP Supt. Martine Fontaine said his relatives co-operated with authorities and it was because of them they were able to confiscate his passport, stop him from leaving the country and implement certain preventive measures.
In the weeks preceding the events, officers had met with his parents and his imam to help change his way of thinking.
"We also used our police officers from the outreach program to help him to see his thoughts were not the right ones," Fontaine said.
The last time police met him was Oct. 9. and Rouleau showed signs of improvement and openness to change following a lengthy discussion.
His father arrived at the family home on Tuesday afternoon and calmly asked reporters to leave him be.
"I want to mourn alone," he said.
Lyse Laroche, 57, has lived across the street from Couture-Rouleau for 24 years. She said he was going under a different name and was the subject of chatter among neighbours.
"He completely changed from the young man that we knew (in) the way he dressed," said Laroche.
She said Couture-Rouleau had a sister and a young son.
"He's always lived in Saint-Jean-sur-Richelieu," Laroche said. "When we heard the news yesterday, we knew it was him — there was no doubt there."
Fontaine said Couture-Rouleau had been known to police since last June.
His Facebook account showed clear signs he'd radicalized and intended to leave the country to fight abroad overseas. He was arrested initially while trying to leave Canada for Turkey.
"The information we had and the statement he provided for us, we (did) not have enough evidence to charge him and to detain him so we released him and continued the investigation," Fontaine said.
Couture-Rouleau was shot by Saint-Jean-sur-Richelieu police after a brief car chase in which his car went off the road and flipped onto its roof.
Brennan, who has family and friends in the military, said he used to hang around with her son when he was younger.
The woman said Rouleau's parents forbade him from associating with her son because they believed he was a bad influence.
"I'm not sure if he moved back in with his dad or what," she said. "As far as I know he had moved out for a while. I hadn't seen him in a while."
— With files in Montreal from Sidhartha Banerjee and Nelson Wyatt
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