" They are military styled assault weapons that are not suited for hunting or defensive purposes."
This statement is incorrect. Rifles are far superior to pistols as defensive weapons, and the rifles in question are superior home defense weapons. They are also used extensively for hunting and competition. In fact, the AR-15 platform is the most popular center fire rifle in the United States today.
Rifles are inconvenient to carry around all day and are usually replaced by pistols for protection outside the home, but they are much more powerful than pistols. And the "hunting rifle" most envision when they hear that phrase is much more powerful than the intermediate caliber rifle used in this crime.