I think Columbine was legit, I was a sophomore in high school in the same district at the time and I never heard anything weird about it on the ground. I think Columbine gave these uncreative assholes their new movie plot though.
Well technically Joe Biden introduced Gun Free Zone act of 1990.
But I knew a bunch of those kids at Columbine, mostly friends of friends (shooters included), but I heard first hand accounts and stories, and those kids were definitely traumatized.
That isn't to say of course that happy pills and focus pills didn't have an effect on the shooters.