Here’s proof that AR-15s are weapons of war

The death toll from the shooting in Colorado may be unusual in most countries, but it’s common in the U.S. because the alleged killer used an “AR-15 style rifle,” a weapon explicitly meant for going on offense and not defense. In this special report, MSNBC’s Ari Melber traces the origins of the weapon and its intended use, how civilians came about using it in increasing numbers, and what makes it so deadly. This is an excerpt from a longer special report.