The tragic shooting of 20 children and six teachers at an elementary school in Newtown, Connecticut stunned people on both sides of the border. Somehow it seemed worse than other recent mass shootings - perhaps because of the age of the children, or the popular military-style assault rifle used, the AR-15. Many hoped it would be a chance to find common ground in a nation bitterly divided over gun rights and gun control. Instead, the sales of firearms soared and the National Rifle Association's membership swelled.