The man who killed a Canadian soldier and then stormed the Parliament in October may not have been acting alone, Prime Minister Stephen Harper said on Wednesday.
Michael Zehaf-Bibeau, a Canadian citizen who wanted to travel to Syria, was shot dead after a gunfight in the halls of Parliament.
"People say he was a lone wolf. It's true he was a single attacker, but it is not necessarily the case that it was only one guy," Harper said in an interview with the French-language TVA network.
Zehaf-Bibeau struck two days after Martin Rouleau, a Muslim convert, ran down two Canadian soldiers in Quebec, killing one. Rouleau was shot dead by police.
"It is possible there were other people around these men," Harper said.
He did not elaborate except to say that investigations were continuing.
In the case of Rouleau, he was known to police for his jihadist views, like dozens of others in Canada, Harper said, but police were not able to arrest them or conduct the necessary surveillance, "and we have to address these difficulties."
Law enforcement authorities around the world are increasingly worried about the risk of "lone wolf"-style militant attacks. While such attackers may cause less mayhem than those backed by militant groups, they are also more difficult to track.
The self-styled sheikh behind a siege at a Sydney, Australia, cafe this week, was considered a lone wolf, according to a criminal defence lawyer who had represented him. Man Haron Monis was killed after police stormed the cafe to end the hostage drama.