The father of Martin Couture-Rouleau says Ottawa needs to strengthen its security laws to deal with cases like his troubled son, a 25-year-old who fell under the influence of radical Islam and killed a Canadian soldier last week.

"What happened was deplorable," Gilles Rouleau said on Sunday from his home in St.-Jean-sur-Richelieu, Que.

Mr. Rouleau says he had alerted police about his son's radicalized behaviour last summer. According to friends and family, Mr. Couture-Rouleau, who converted to Islam in 2013, began to embrace extremist views and fall under the sway of jihadi ideology on the Internet. He used the handle Ahmed Rouleau on his Facebook page.

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Federal officials began to monitor Mr. Couture-Rouleau and arrested him in July as he was preparing to leave the country for Turkey, a jumping-off point for jihadis bound for Syria, but released him after prosecutors determined they didn't have evidence to charge and detain him.

Gilles Rouleau says the Canadian government needs new rules for such cases.

"Change the law, change the law," Mr. Rouleau said in brief comments on Sunday. "Right now, if you have a problem in your head, and your family says you're not well … they say 'we can't do anything'."

"That's what happened," Mr. Rouleau said.

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He called on Canadian law-enforcement to use some kind of psychological test to evaluate high-risk cases like his son.

The Harper government is planning changes to national-security legislation and says it wants to step up police powers over surveillance and detention and is considering changing the threshold for preventative arrests.

The RCMP says Mr. Couture-Rouleau was identified as a high-risk traveller put on a watch list as a possible Islamic extremist. They had spoken to him as recently as this month but had no grounds to arrest him. "We could not arrest someone for having radical thoughts. It's not a crime in Canada," RCMP Supt. Martine Fontaine said at a press conference last week.

Mr. Couture-Rouleau struck two members of the military with his car in the parking lot of a shopping centre in St-Jean-sur-Richelieu that houses offices dispensing government services. The attack killed Warrant Officer Patrice Vincent, a long-serving member of the Armed Forces.