Re: @ scarletherring
In a "gun-free zone", anyone wanting to go on a rampage in a school/college/cinema/shopping mall would generally have to find another (ultimately less effective) weapon instead of just going and opening their own/parents/friends gun cabinet.
However you'll also notice that in a gun-free zone, the chance of a parent being accidentally shot by their own child drops to zero (a couple of recent cases spring to mind, one in a supermarket and one whilst the mother was driving). As does the chance of a child accidentally killing themselves (another recent case where the child was at the grandparents house and found a loaded pistol). As also does the chance of someone accidentally shooting and injuring themselves (no citation needed, just search YouTube).
Gun issues aren't just a US-specific issue, however having access to firearms makes anyone more dangerous. Oscar Pistorus would be an example of this in a non-US context - the simple fact that there was a legally held gun in the house, along with a "shoot-first" train of thought had tragic consequences.