NZ security agencies failed Christchurch - Joseph Siracusa

A global security expert says New Zealand's intelligence services failed the country by not picking up the accused gunman earlier. Professor Joseph Siracusa from Melbourne's RMIT University says any successful terrorist attack is a failing by intelligence agencies or, in many cases, the police. Philippa Tolley asks if it was possible for any agency to be 100 percent successful in foiling terrorist attacks.