This is not the time to meekly assume restrictions ARE coming, and start negotiating the terms of our surrender. Now is the time to dig in to defend our position.
The guns involved are merely the tools used. The problem goes much deeper than that, and the question is one of why in the last three decades these incidents started occurring?
Let's look at the changes in policy (at the school level), in the assumptions made about behaviour, in the ways of dealing with those behaviours from an early age, not just by schools, but by parents and other organizations and see what has changed to foster an environment that makes little monsters who go back to the schools to shoot the place up. Why the schools and not shopping malls or grocery stores?
Because that's where the anger is seeded and grows.
This appears to be as much a developmental issue as anything else, perhaps more so. Medication does not lead to development, nor (apparently) do current policies. Granted there are cultural influences as well (music, media, etc.), but the root of the problem is where the anger is being taken out. Start looking there.