I'm totally opposed to U.S. gun laws.
There has however been a notable number of similar shootings in other countries like germany, though its nowhere near as high as U.S. So its not just an US problem. One might even argue that it might just be that high in the US because US has a vastly higher population, making it more likely for those indiviual shootings to happen - though there is no denying that lax gun laws are very likely to increase the chance of something like this happening.
Even in those cases from non-US shootings, from my information there has always been legally owned guns in play, I can't really recall many (school) shootings in non-US western countries that where conducted primarly with illegal weaponry, so I think there is a good point in restricting the possesion of guns to combat this problem.
And yet, Chicago has some of the strictest guns laws in the nation with the highest rates of murder and gun crimes in the nation. This isn't a gun issue, it is a people issue. If we abolished gun ownership and somehow managed to confiscate all guns and melt them down, there would be mass stabbings or bombings. If someone is intent on causing this level of harm to others, they will find a way. You cannot legislate away evil, no matter how hard you try.