Hmmm...If I'm reading your statistics right, since 2004 there has been a decrease in murders in the US. So, from your statistics, just as much of that decrease has happened since President Obama took office - yet he is a commie pinko who wants to take our guns... 

But that is beside the point. Your statistics omit possible correlative factors such as a rebounding economy, because we all know that murder and the decision to murder does not occur in a vacuum. Also, your statistics are not directly related to mass shootings on school property, but murder in general, which has all number of tools of the trade, if you will. Finally, you appear to be trying to connect lower murder rates with higher instances of an armed public yet the statistics presented don't support that claim, nor do the overall numbers if you were to look into them at all. The states with the highest instances of gun violence (all gun violence) also happen to have the highest gun ownership.