Moscow attack: US, Canada had warned Russia of imminent terrorism risk prior to shooting

In Russia, all four gunmen behind Friday’s attack on a concert hall on the outskirts of Moscow have been arrested. At least 133 people are now known to have been killed in the terror attack. The Islamic State’s affiliate in Afghanistan has claimed responsibility. As Mike Drolet reports, the U.S. and Canada had recently warned Russia that “extremists” had imminent plans to target large gatherings.