[@The Harbinger of Ferocity]
I wouldn't dismiss Penny's comment completely out of hand, as blunt and reductionist as it was. American politically motivated attacks on either side of the spectrum are far more commonly reported than from other western countries I can think of. I would struggle to think of any instances of 'domestic terrorism' in my own country or within Europe, but I could probably name five American instances off the bat. You can put that down to a lot of things. 

However, if we can believe the information that has been released so far, it would be hard to draw the conclusion that this instance could have been prevented with tighter gun control.