Just equip every American over the age of 12 with a gun and this won't happen, no shooter will be able to get more than 2-3 kills before getting shot, simple as
Edit: Just read this happened at an elementary school, make it from age 6 then
Actually never mind, it seems that the one in Buffalo was not last week, but the week before. Unless I missed something, they didn't have any major ones last week. Breddy good by Murrican standards.