Cross Border Gun Tragedies

As both sides of the Canada/US border have been struck (Denver) by large incidents of gun violence (Toronto) within a short time span, I suppose it is natural that many (at least in Canada) are connecting the two events.  There are obvious similarities (large numbers of victims, the pointlessness of it) but important differences too (most of the victims in Toronto were unintentional, the result of cross fire between fighting parties, whereas in Denver we are talking about a lone shooter intent on deliberately killing as many as he could).

But to the extent they are similar, I have two comments for the gun-proponent crowd: 

• Is there anything that would have been better about either shooting if more people in those crowds had been armed?  Is there any realistic chance an armed "law abiding citizen" could have done anything but add to the mayhem and victim count by drawing yet another weapon and opening fire?  In Toronto you already have multiple (possibly 3 or more) shooters firing at one another.  Who are you going to shoot?  What  In Denver, you're in a crowded and dark movie theatre, and there is some kind of tear gas or smoke grenade making it very difficult to understand what is going on.      

• Where is the deterrent effect?  In both cases, the shooter(s) had a pretty reasonable expectation that one or more of his targets could or would have a gun to shoot back.  Colorado is not a strong gun control state.  Obtaining a concealed carry permit is easy.  Open carry of handguns is even legal. This was not a school or some place which searches patrons to prevent guns getting in.  Why didn't this dissuade the shooter?  For that matter, where were the armed civilians to save the day?  Where are these supposed anti-crime benefits of lax gun laws?  Gun proponents suggested the Virginia Tech shooting might have stopped if not for a campus rule prohibiting guns, what's the excuse here?   At what point do we start asking when at least one of these mass murder situations will actually be stopped by an armed civilian?  As for Toronto, the (as yet uncomfirmed) rumour is that the shooters were gang affiliated and if so, had every reason to expect their targets were armed.  Which is generally the case for "gang" shootings:  If gangsters are not scared off engaging in gun fights with their fellow "hardened criminals" known to both possess and be willing to use guns, what makes anyone think criminals are much afraid of armed civilians when contemplating crimes?  Where is this supposed deterrence effect of an armed populace?   

If anything, it appears the shooter in Colorado simply accounted for the possibility of return fire from his victims by wearing armour and using some kind of smoke/gas grenade to create confusion.  Is this the "benefit" of an armed populace, simply better armed and prepared mass murderers?

And while it's true Canada's gun controls did not prevent the Toronto shooting, by the numbers there's just no comparison to US gun crime or general violence levels.  Is there any reason to expect that Canada relaxing its gun laws would lead to anything but more such shootings, without any of the promised upsides of widespread civilian gun ownership and carrying?