“Terrorist attacks are intended to be public events. We quickly know what happened and where, but unless the terrorists accompany the attack with a claim of responsibility and an explanation, figuring out who did it, why they chose a particular location or target and what they hoped to accomplish are often matters of informed speculation. So why did terrorists attack the Russian city of Volgograd?
Circumstantial evidence supports the widespread presumption — although it is still a presumption — that Islamist extremists who have been challenging Russian rule in the Caucasus are responsible. Most likely, they are fanatics connected with the shadowy Caucasus Caliphate. This latest, and more Islamist incarnation of the Chechen resistance movement has been responsible for a continuing campaign of terrorism across Russia. Its leader, Doku Umarov, has declared his determination to disrupt the forthcoming Winter Olympics in Sochi, even at the cost of innocent civilians, so bombings in public places just six weeks in advance of the event make his outfit a prime suspect. But in this turbulent part of Russia with its mosaic of conflicts in Chechnya, Dagestan and Ingushetia, motivated attackers are plentiful.”
Source: Why Did Terrorists Attack Volgograd, Russia, Before the Olympics? – World Report (usnews.com)