Sorry but that is completely and utterly irrelevant to what happened at Dunblane
Well, then all we have are duelling anecdotes. But consider this: if Myrick had not inadvertently left his gun in his car, and the kid's friends had continued the carnage as they had planned, would gun control people not be saying EXACTLY the same thing that you are? "Hey, if they didn't get guns, how could they have done that?" and completely dismissing the possibility of one armed person stopping it (as is what actually happened).
I also suggest that had Luke Woodham NOT had a gun, the death toll that day would have been lower.
And I suggest that no amount of gun control would have stopped him from getting a gun if he really wanted one.