Separate opinion on the Beslan tragedy

This programme deals with the 2004 Beslan hostage crisis. In September 2004 a group of armed terrorists took hostage more than 1100 people in a school (including almost 800 children). The 3 day long crisis ended with a bloodbath. Now, 3 years after the event, the question remains: who is responsible for the killing of 334 hostages? What were the mistakes of the security forces?