That's a terrible story, involving some sick people.
The same laws and regulations that apply at any gun or sporting goods store also apply at Walmart. The story you posted displays that guns aren't the problem, sick people are the problem. They used metal bed posts and dogs to assault the lady. The mention of guns being sold at Walmart has no relevance here, or anywhere, really. I'm in IL, where guns are not sold at Walmart, and you can believe me when I say that Walmart not selling guns does nothing to thwart gun violence, and if they did sell guns, the gun crime statistics wouldn't change.