Just because it hasn't been reported of any group taking responsibility doesn't mean noone has, it just hasn't been released, same with vid and pics. They don't want anyone ther than a white, right-wing nutjob (aka OSA member) and will only release what will back their plan. Otherwise, this will go the way of Bengazi and media attention diverted elsewhere .......... Ricin letters, Fertilizer plant explosion, what ever the next catastrophy they have planned is ........... whatwever it takes to pass gun control and keep the people safe.