When it comes to what happened in Isla Vista, I doubt I can say anything that hasn't already been said. But there's one point I want to record for posterity because it's common to so many of the social problems we face, and I'll inevitably need to refer some folks to it.
Saying that this was an isolated incident, or blaming it solely on a single person's mindset, is how you dismiss the underlying problem. And as long as you keep treating these events as one-off random occurrences perpetuated by irrational people, you will continue ignoring that problem.
As soon as you recognize and acknowledge the pattern -- as soon as you see the commonalities between different incidents and the factors that underlie them -- you will have named the problem and taken the first step towards solving it.