There is something that seems different about what is happening now versus atrocities of the past. Now killing is happening for the sake of killing... no other motivation other than too kill... no ideology but blood lust. There are probably examples in the past of this but honestly, the earliest example I can think of is Charles Whitman. Regardless it seems to be escalating, every act more heinous, more incomprehensible.
We need to put back into our world what the sick and twisted are trying to take away from us. We can't do anything about what they do. But we can control our own actions. There is no way to respond to acts like this other than countering them with our own acts of love, compassion and kindness. Sounds hokey perhaps, but there's something wrong out there, and we all need to step it up.