"America's most popular rifle, the AR-15 is at the center of the debate on gun control raging through the United States. As the smoke clears from a shooting at Los Angeles International Airport this morning, there appears to be a familiar rifle laying on the ground by the feet of officers and first responders — an AR-15. Los Angeles' ABC News affiliate confirms that the weapon was indeed an AR-15, and images of the scene indicate that, as well. It was also the weapon of choice for James Holmes in Aurora, Colo., and Adam Lanza in Newtown, Conn."