Canada: Man strikes 2 soldiers, kills 1

• NEW: Royal Canadian Mounted Police: Suspect was "radicalized"


• NEW: Man's passport was seized in July before he went to Turkey, police say


• NEW: The man allegedly ran down two soldiers on foot, killing one of them


• NEW: Police say they shot and killed the man after a car chase

(CNN) -- A man shot to death after running down and killing a Canadian soldier with his car was "radicalized" and classified as a "potential important threat" to the country, Canadian authorities said Tuesday at a press conference.

Police arrested Martin Rouleau Couture, who reportedly converted to Islam about a year ago, last July and confiscated his passport, but lacked enough evidence to keep him in custody, said Martine Fontaine of the RCMP.

"When he was arrested, he was about to go to Turkey," Fontaine said. "We stopped him as he was about to leave Canada for terrorist actions. He was questioned when he was arrested. We have not been able to determine any real threat at this time."

On Monday, a man driving a car hit two members of the Canadian Armed Forces who were walking in a strip mall parking lot in Saint-Jean-sur-Richelieu, Quebec, said David Falls, spokesman for the Royal Canadian Mounted Police.

One soldier was killed

One soldier died and the other was injured. The suspect led police on a chase before his car rolled into a ditch in the town, southeast of Montreal, Falls said. Police said the man exited the car before officers shot and killed him.

Months ago, Couture's parents saw a change in their 25-year-old son's behavior and asked authorities for help, police said.

"He was identified as a potential important threat," Fontaine said. "His Facebook profile showed that he was about to leave the country and that he was radicalized. We met him several times. We worked with the imam of the mosque he was going to."

Fontaine said police monitored his activities afterward.

"It is very difficult when a person prepares an act alone and uses a vehicle as a weapon," he said.

Police said there are about 90 people in Canada classified as important threats. Bernard Lamotte of the RCMP said a unit formed in 2003 keeps an eye on potential terrorist activities.

"Each threat is taken seriously," he said. "The threat that represents the Islamic State is taken very seriously."

'Remain vigilant and suspicious'

"We are still investigating on the radicalization among Canadians," Fontaine said. "We continue to promote a relationship of trust among Canadians so that they feel encouraged to share their concerns.

"We encourage families to remain vigilant and suspicious. The threat is real. We put everything in place to ensure national security."

The two soldiers were from the town's Saint-Jean Garrison.

"I want to express that the authorities can count on our full support in order to get to the bottom of this terrible act," Prime Minister Stephen Harper said Tuesday in a written statement.

Neighbors told the CBC's French-language service that Couture converted to Islam about a year ago.

The news comes as Canada gets more involved in the global fight against the Islamic State in Iraq and Syria, also known as ISIS or ISIL. Canada has pledged the use of fighter aircraft against the radical Sunni militant group taking over swaths of the Middle East.

Holly Yan, Paula Newton and Jennifer Moore of CNN contributed to this story.