Harsha de Silva on the Bombings in Sri Lanka

In Sri Lanka, hundreds are dead after a brutal series of coordinated bombings on Easter Sunday. It is among the most lethal terror attacks since 9/11 and is the worst violence in Sri Lanka since the bloody civil war ended there ten years ago. With the US government tying the attacks to ISIS, Christiane asks Harsha de Silva what the Sri Lankan government knew, and why it failed to act.