You Americans amuse me to death. Keep on telling yourself your mantra of staying passive about all this: How it's single incidents, how people kill people not guns, how the press writes it up, how criminals always get guns (funny thing is: they generally don't waste their bullets on kids), how more death penalty will deter these people, but sensible gun laws won't. And how you are a young frontier-influenced country where things like that take place, you're only a little under 240 years old, surely things like that are meant to happen then. Also it's an Amendment. And people for tougher gun laws are likely for more gay marriage too, so we all know where this is coming from.
Until a few months from now when it happens again, you drape the coffins in the flag and NOTHING happens in the aftermath.
This has nothing to do with party politics and everything with common sense and human experience. That laissez-faire libertarian view that nothing can and/or should be done is as coherent as legalizing crystal meth. That won't kill responsible users either and the criminals already get it anyhow ...