In the late 60's and early 70's I took a gun to school twice a week for rifle club practice at the schools indoor range. This was in Pennsylvania. You could bring your own ammunition or buy it at a discounted rate from the school. The zero tolerance firearms policy meant that you did not get a second chance for a violation of firearms and range safety rules as taught and enforced by NRA certified instructors and coaches.
I am now over 6'1" and about 225 lbs. but I was on the small side in school, only 5'10" and 145 lbs. at graduation. While in school, there were times that I was bullied by older, larger kids. It never once occurred to me that I should bring my rifle or any of the other guns that I had easy access to, and shoot the bullies. None of my many gun owning classmates ever even talked about bringing a gun to school to shoot someone. Nor did we ever hear of school shootings anywhere else. So what has changed?
I have noticed a frequent common thread that very often accompanies these mass shootings. I have also read about it, but for some strange reason, it gets scant attention. Very often, the shooter is either on anti-depressant medications, or has very recently been taken off of them. Prozac, Paxil, Zoloft, Effexor, Amitryptyline, and other related prescription drugs appear to be strongly linked to murderous rampages. Columbine's Eric Harris was on Luvox. The killer at Virginia Tech was on anti-depressants. Try Googling "Anti-depressants mass murders" and similar searches for some eye opening reading. The commonly used ADHD drug Ritalin or Ritalin in combination with an anti depressant has been implicated in violent behavior as well.
Something is amiss here. None of this is a secret, but this link between certain prescription drugs and mass murder does not get the press and publicity it deserves. The blame for these rampages is often directed at the availability of firearms when the real cause may be the drugs that the killers have taken. This link needs to get more publicity, but the press generally would rather blame the guns, I believe. Check this out. You'll be amazed.