I can't say I'm personally against the restricting the sales of guns due to action of one individual in Colorado who lacked rational sanity, however, I could respect one's wishes to place into effect sanity checks in sales of firearms, better monitoring in sales, or even something as small as restricting mass purchases without first identifying the pacific areas you used your provided weapons.
I don't feel guns are the problem, but, people are. People kill people, not guns. That already became relevant when guns had been banned within the country of Australia and restricted to the hands of officers and military personnel. Crime rates shot through the roof, including those of rape and listless burglaries.
Even if you ban the weapons, people are still able obtain them illegally in first place. It is not as if one is not able to spend of bit of money to gain this weapons in the first place. All these weapons per unit can be worth up to several thousands.
Regardless, I would personally believe it's Canada's responsibility to regulate weapons within their own state. That of course would require funding if on were truly concerned about find a "solution". I'm not sure what else I could say.
--—Frenchbread is ♥