A lot of people—including most of the news media—are completely ignorant of the difference between fully automatic weapons (machine guns) and semi-automatic (self-loading) firearms.
This video explains the difference, and should be required viewing for anyone who thinks that the AKMs or AR-15s sold in gun shops are “machine guns.”
The fact of the matter is that the manufacturing of automatic weapons for the general public has been tightly regulated for 80 years, since 1934. Because of this there have been just two criminal homicides committed with legally owned automatic weapons and two accidental shooting deaths with legally owned automatic weapons (including the recent range employee shooting in Arizona) in the past 80 years.
Fully automatic weapons have not been manufactured for the general public at all in 28 years, since the Hughes Amendment to the Firearms Owners Protection Act became law in 1986.
There has never been an American murdered with a legally owned assault rifle (intermediate caliber, selective-fire) in the history of the United States.