The first comment after the article made me chuckle...
Ft Hood - Registered Democrat; Muslim; not an NRA member

Columbine - Both too young to vote; but families were registered Democrats; liberal-progressives; not NRA members

Virginia Tech - Wrote hate mail to GW Bush & staff; registered Democrat; not NRA member

Colorado Theater - Staff worker for the Obama campaign; ‘Occupy Wall Street’ participant; registered Democrat; liberal-progressive; not an NRA member

Connecticut School Shooter - Registered Democrat; hated Christians; not an NRA member