Just FYI, the violence of mass murders is not increasing. Neither anti-gunners nor pro-rights people can say that it is.
I base my assertion on the data in Grant Duwe's book Mass Murder in the United States, which tracks mass homicides going back to 1900. Despite common perception, mass murders have been common throughout American history, and have closely followed the trends for other types of crime.
Incidentally, the most deadly attacks have used weapons other than guns.
What did you base your assertion on?
My personal website: Cornered Cat