Originally Posted by Rochard

Maybe - depends on the intentions of the shooter. If the shooter is well armed and has a lot of ammo, and his intention is to kill as many people as possible... The armed guard MIGHT be able to prevent a lot of people from being killed. On the other hand if it's a fourteen year old kid who pulls his gun out because he's mad at one person during an argument then it will already be over before the armed guard gets there.