Making the dangerous assumption that a prescription indicates that a doctor is actively monitoring the person, I find this to be very preferable to having someone self-medicate. The tower shooter in Austin, TX was a alcoholic, other school shooters have used other drugs.
The one part of the profile for school shooters that I am waiting to see come out, loner and depressed are already there, is the obsession with violent video games, movies, or songs, or possibly all listed.
I think the brain tumor was a bigger factor than his drinking...