The MOST interesting statistic is revealed on the 'interactive' at the article at the title to this entry.

Gun crime in the US: victims killed at a political event where Gabrielle Giffords was also shot in Tucson, Arizona. Photograph: AP

When one toggles (at the interactive map of the USA) between "Total Fire Arms Murders" (the first title at the down arrow in the left upper corner) and "Handguns" (the second title at the down arrow in the left upper corner) there is virtually NO difference.

In other words, where there are sales of HANDGUNS, the number of murders by firearms is DIRECTLY proportional. 

It has NOTHING to do with gun laws.  

It has everything to do with GUNS.