Taking guns away from the people who know how to use them and are responsible with them solves nothing...because they crazy people who want and/or need and/or have a desire to kill people will find guns to do it with.
You'd be reducing the numbers tremendously though of incidents like this, if you want to get a gun on the street its not just about having money, you have to have connections and put yourself in dangerous situation to acquire them. Places that are usually under survellance and would lead to foiled plots often. I'll stop after this reply because this incident is tough to even talk about.