How Would Gun Control Reduce the Number Of People Who Are Murdered With Guns?

With 70 people shot in a movie theater in Aurora, Colorado - 12 of them dead, including a six-year-old girl - some people are predictably blaming the gun laws (or lack thereof) and calling for more “gun control.”

I don’t understand this. If a person is willing to shoot 70 people, how likely is it that guns being illegal will keep them from obtaining one? With at least 200 million guns in the U.S., it’s never going to be difficult to get one, legal or not. I don’t...