In the wake of the Newtown massacre on December 14, gun control advocates are focusing on the weapon used by the killer and by others before him.

When Adam Lanza, 20, gunned down 20 children and six adults at the Sandy Hook Elementary School, the firearm he used was an AR-15 assault rifle.

The AR-15 was also employed by James E. Holmes, 24, the man accused of killing 12 people in a movie theater in Aurora, Colorado, July 20.

Jacob Roberts, 22, who shot and killed two people before taking his own life in a Happy Valley, Oregon, shopping mall on December 11, also used an AR-15.

The AR-15 is the most popular rifle in the U.S., purchased by hunters and gun enthusiasts. It was first developed in the early 1960s, and has been used by the U.S. military (as the M16) since the Vietnam War.

Gun control advocates want something done to curb the AR-15s use by killers like Lanza. One point of focus is to ban the sale of high-capacity magazines for the weapon that allow shooters to fire off multiple rounds in very little time.

Congress banned the civilian use of assault weapons in September 1994, but the law lapsed in 2004 and was not renewed.

Opponents of banning AR-15s argue that it is pointless to legislate a single weapon or accessory. They point out that Lanza was carrying a 10-millimeter Glock and a 9-millimeter Sig Sauer in addition to the AR-15. Similarly, Holmes had two Glock handguns and a shotgun with him during his killing spree.

Furthermore, Seung-Hui Cho killed 32 people and wound 17 at Virginia Tech in 2007 while using a Glock and a Walther, and no AR-15 at all.

-Noel Brinkerhoff

To Learn More:

Rifle Used in Killings, America’s Most Popular, Highlights Regulation Debate (by Erica Goode, New York Times)

AR-15 (Wikipedia)