I don't know, but i doubt the answer will be found here, and if by some miracle it is found here, there is little hope that the solution will be implemented.
I do know the answer isn't to take rights away from millions of law abiding citizens because of a hand full of nut jobs who are clearly mentally unfit to be a part of a society full or or without guns.
People are very quick to say don't judge all muslims by the extremists. Same goes here; don't judge me by what a mere fraction of a fraction of what the gun owning population does.
"Government is the great fiction, through which everybody endeavors to live at the expense of everybody else." — Frédéric Bastiat