The effluvia emanates from the Gun Violence Archive. I've set the link to the methodology page. You can click back to their home page from that link after reading the BS behind the numbers.
Don’t know if you’ve seen this or not. Weird they need a “handbook” to get their lies, uh, message out huh?
http://s3.documentcloud.org/documents/748675/gun-violencemessaging-guide-pdf-1.pdf
See if you can see any of there “suggestions” at work in the press.