There is one thing, in regards to the original post; Even in the U.S., there are not very many instances where a CCW or civilian pulled a gun to stop a shooter. The only famous one I can think of off of the top of my head, is the U of T observation tower shootings' in 1966.
In the report afterwards, one of the local P.D. officers' gave credit to the armed civilians. He stated that their fire made Charles Whitman keep his head down, thus making it hard for him to further kill anyone else.
But, he still killed 14 and wounded 29, as of that morning. No, the civilians' weren't shooting each other. They knew who the gunman was; All of the fire was coming from the observation deck of the tower. But, the civilians' weren't able to stop Whitman by themselves. Two cops (and one hastily deputized citizen) went up to the observation deck and killed Whitman.
From the U of Texas' shootings, it's really kind of hard to tell if an armed populace had much impact. The police report does credit them, but Whitman's rampage was very deadly anyway.