Rick Hanson said al-Qaida made it clear several years ago that Canada was at risk, and that view was reinforced recently in statements from the group Islamic State encouraging attacks on Canada.
The concern now is that others may be inspired by the hit-and-run attack on two soldiers in Quebec and the shooting of a soldier near Parliament Hill.
"One of the biggest risks that exist is copycat activities," the chief said Wednesday.
"Right now, this week, there has been two very high-profile incidents that occurred. We know from events that have occurred elsewhere in this country at various times, that you have to be fearful of copycat offences. Are we aware of that? Are we communicating that? Are we more vigilant to that risk at this particular point in time? Absolutely, we are."
There have been reports that a handful of young men with Calgary roots have been radicalized and gone to fight overseas with Islamic State.
Calgary mother Chris Boudreau has spoken openly about the need to reach out to youth after her 22-year-old son, Damian Clairmont, converted to Islam and was killed while fighting with the extremists in Syria.
Hanson said he doesn't believe Calgary is any more at risk than any other Canadian city.
He said police are aware of some individuals who may be a risk to national security, but it would be foolish to assume they are aware of everyone.
"Are we surprised that this event today happened in Ottawa? Not at all surprised," he said.
"The reality is, if we are surprised that an act like that happened or could have — and I want to stress could have — terrorism implications, we'd be pretty foolish to stand up here and express surprise when it has been so overtly stated for so many years that Canada is a target."
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