Below is an interview with John R. Lott, University of Maryland research professor, formerly a senior research scholar at Yale Law School and previous John M. Olin Law and Economics Fellow at the University of Chicago. Dr. Lott is the author of More Guns, Less Crime and Straight Shooting.
Dr. Lott has looked at statistics around gun control and come to the simple conclusion that guns lower crime rates. He discourses at length on that topic and how it relates to Washington D.C.'s horrific murder rates in this interview on CSPAN:
Says Lott, ". . . if you look at the types of multiple-victim public shootings . . . one thing that you continually find is that they take place where guns are banned in the United States . . . all the attacks in the United States involving more than three people killed have all taken place in gun free zones where civilians are not allowed to take guns . . . rather than creating safe zones for victims, what you unintentionally do [with gun free zones] is create a safe zone for those intent on carrying out the attacks . . . " This isn't news to those who've been paying attention, but Lott brings the research to back up his claims.