I worked for the local school system a year ago and I was amazed at how
easily people could walk into and out of our local buildings through a
variety of doors and open windows. Pre-Columbine schools weren't designed
with security as the primary factor. So it all comes down to the desire of
the potential shooter. If they truly feel no remorse about taking the life
of another human being, and they don't fear their own deaths, then there's
really nothing to stop this horrible tragedy from happening again and again.
God help us all.