I always try to look at things from both sides. I've heard different arguments from both sides of the whole gun debate that raise good points. For example, the cinema apparently banned the carrying of firearms in the building. That left the law abiding people who normally carry guns unable to do anything. There is also the fact that in most US states, in order to carry a concealed firearm you have to get a license, for which you will have to take training courses and such so that if you needed your gun you would be able to use it effectively. People who would have been legally carrying a gun wouldn't have just started popping off shots in the direction of the shooter, and would have been thinking about the fact that they might end up shooting bystanders by mistake.
On the other hand however, this took place in a dark and noisy place. The guy had set off smoke grenades. Most people would have been confused as to what was happening, they couldn't really see the shooter, and all it would have taken is one guy carrying a gun with too much faith in his abilities to cause more harm than good. Also, the sound of gunfire from
more than one direction might cause problems with people trying to figure out what direction to escape, or for police responders.
In other words, carrying a gun might be a good idea for someone expecting to be mugged, or wanting to defend their homes, but in a mass shooting it would probably only cause harm. In a case like Columbine, where the shooters stayed on site, wandering around looking for people hiding, then someone with a gun might stop the attack. One, or few targets, moving slowly, no other people nearby, in danger of being hit, then someone carrying a gun could help. But that only happens in rare cases, and police responders are usually quick enough to negate this point. Someone carrying a gun might feel they should use it, when it wouldn't help the situation.
This isn't even taking into account how easily the shooter got hi weapons.
In short, gun control isn't really a black or white issue.
My personal opinion is that guns should be legal, but only accessable to those who have gone through evaluations and training. Probably more training than is currently required for concealed carry weapon permits.
I would actually like to own a gun. I seem to be good at target sports. I enjoy archery, and my experience with pellet guns has been positive, so I would be just as interested in target shooting. However, I would consider it perfectly understandable if that wasn't considered a good enough reason to own a gun, and was denied a permit. The fact that permits and such are required means that gun crime is quite rare in Ireland.
However, it should also be considered that outright banning guns wouldn't work for the US. Guns there are widespread. There are lots of places where you can buy a gun without it being registered. There are many, many illegally owned guns in the US, many owned by criminals who wouldn't be afraid to use them. The government couldn't take them off everyone without searching every single building from head to toe. If they were banned, only the law abiding gun owners would hand them in, leaving them unable to defend themselves from those criminals who kept theirs. Gun control and regulation is a good thing, but in a country like the US, it would be extremely difficult to implement.
/myrambling2cents