If someone wants to kill lots of people, said person will kill lots of people, regardless of the laws. Making guns harder to legally be obtained is not the proper way to go about it, because there are ways of illegally obtaining guns.
If more people exercised their rights to have guns, there would be less shootings, because more people would be able kill the shooter before they start shooting up the place, or the shooter will hesitate to even do it in the first place, out of fear he'll get shot right away.
The fact is the United States is littered with guns, & taking away a legal way of obtaining them only hurts the "good guys."
Chicago has the strictest gun control, if you want a frame of reference.