A 1996 study at the University of Chicago, a 2003-04 study by the U.S. Health and Human Services and the Centers for Disease Control and Prevention, and a 2009 Harvard study all concluded that there is insufficient evidence that gun control reduces gun violence. Both Washington, D.C., and Chicago have strict gun control laws and extremely high gun-murder rates. Since 1950, with one exception, every mass shooting where more than three people died occurred in a gun-control zone.
These facts are found under "Stats and Services" — "Crime Statistics/UCR" on http://www.FBI.gov. Assault weapons are rarely, if ever, used in gun crimes. In 2011, assault weapons accounted for less than 2.3 percent of murders, and gun crime has fallen since the assault weapons ban was lifted in 2004.
According to a Wikipedia listing of the more than 90 school shootings since 1990, I only counted two where assault rifles have been involved. It is delusional to think any assault weapon ban will prevent gun violence. All it will do is deny law-abiding citizens the right to own them.
Some people say, "Nobody needs a gun like that," to which I reply, "The moment we let other people decide which rights we need and don't need, is the same moment liberty dies."