That's not a question, it's a textbook example of the complex question fallacy, which is dishonest rhetorical trickery. Also useful if you just want to insult someone but pretend you're asking a question. If a person was just interested in the guys relationship with his brother, they'd ask "how come your relationship with your brother is so trash?", without the loaded accusation at the end.
It's the same category as "so, have you stopped beating your wife yet?"
No, you open up the Chrome Dev Tools, click the Timeline tab and then start recording. Click a few days in the calendar, stop the recording and then you'll see that after each click it takes 100ms until paint events are shown.
Note that in the Pearl High School shooting (item #1), Assistant Principal Joel Myrick had to retrieve his gun from his truck parked off campus because it had to stay outside the "gun-free school zone". It's unclear how many of the 9 victims could have been avoided but for the "gun free school zone."
Ok, so there are some cases where it helped stop the attack. Going a step further, how many of those had AKs and maybe bullet proof vests? Should everyone have armor piercing bullets too?
How many of the attacks happened because it was easy to get guns in the first place?
A terrorist will always be able to procure guns. But what about an unhappy employee, an angry teenager ?
No, having guns won't help one bit. Just name one attack in the States that has been foiled by a citizen.
What will happen unfortunately is that the surveillance measures will increase exponentially, normal citizens will throw privacy out the window, terror attacks will still happen.
It happens quite frequently. If everyone had a gun it would prevent almost all of the incidents. I'm not sure why you would argue this. The other question is how bad is the result of everyone carrying a gun.
