Source: Ottawa gunman communicated online with extremists

CNN has learned the gunman responsible terrorizing the Canadian capital Wednesday, shooting and killing a soldier, had ties to jihadists.

Michael Zehaf-Bibeau's terror connections appear to have been online. Officials say he used social media to communicate with at least one other extremist who went overseas to fight in Syria.

In light of the Ottawa shooting, CNN's Tom Foreman explores the dangers posed by lone wolf attacks.