American gun policy is a deadly compromise.
Pro-gun advocates explain that the Virginia Tech killer would have been stopped in his tracks if students and teachers were carrying concealed weapons. This is absolutely correct -- it is obviously much harder to kill people who are armed.
Meanwhile, gun control advocates explain that those murders would never have happened if the killer could not get guns in the first place.
The is also completely correct -- just look at the murder rate in Asia and Europe to see how limiting access to guns reduces violent crime.