Canada is in shock. Twice in three days, recent converts to radical Islam have carried out attacks in this usually peaceful nation. Were this week's attacks avoidable? Will more follow in places like France and Germany, which - like Canada - have this time joined the anti-IS group coalition after sitting out the 2003 US-led invasion of Iraq?
Former Canadian government official
Foreign editor at The Daily Beast
Head of outreach, Quilliam Foundation
Professor of Law, Georgetown university