One item (and photo) from a list that is many screenfuls long:
>>August 11, 2009--William Kostric is filmed openly carrying a handgun outside of President Obama's health care reform town hall meeting in New Hampshire. Kostric holds a sign that reads, "IT IS TIME TO WATER THE TREE OF LIBERTY!" a reference to the following Thomas Jefferson quote: "The tree of liberty must be refreshed from time to time, with the blood of patriots and tyrants."<<
Please review this as a basic background document on considering the possibility that a tone of extremist rhetoric could be related to outbursts of political violence -- or, more constructively, whether one response to this tragedy should be deliberate cooling down of political talk.