Wikipedia has a list of school-based rampage killings. You’ll notice that the majority of those incidents listed occur outside of the US. If you further investigate, you’ll notice that all of those countries that are not the US have very strict gun control laws (typically, individuals cannot own guns, and if they can, cannot take guns outside of their houses). So, practically, gun control would appear not to be the proper response to the recent killings; at least, not if you want to save lives.
Furthermore, there are profound philosophical and political reasons why gun control is not the answer. The Swiss Economist does a good job highlighting (some of) these reasons through a series of quotations.
Thinking is the proper response, not jerking one’s knee.