https://twitter.com/rfield701/status/379813432624545793

https://twitter.com/AdamBaldwin/status/379817550810337282

AR-15 is a "genericized trademark" describing rifles that are based on a design developed by Armalite and later sold to Colt. The AR-15 was originally built as a smaller, lighter version of Armalite's AR-10, chambered in 5.56 NATO round. The AR-10 is chambered in the larger 7.62 NATO. Armalite later sold the rights to the AR-15 design to Colt.

While there are some companies that claim to make an AR-15 style shotgun or AR-15 upper receivers chambered for a .410 shotgun shell, not only have I never actually seen one, but there has been no information to indicate the shooter had such an uncommon firearm.

Twitter was quick to ask CNN where one of these "AR-15 shotguns" could be found:

https://twitter.com/red_red_head/status/379812005848178688

http://twitter.com/gwshark11/status/379799054328147968

https://twitter.com/MikeBeas/status/379813919327780864

https://twitter.com/jacks4118/status/379811136948170752

https://twitter.com/Ryster99/status/379767864976093185

Others wondered if CNN was pivoting into the comedy market:

https://twitter.com/robtr2/status/379821430709293056

https://twitter.com/NathanWurtzel/status/379805352226586624

https://twitter.com/JaiSimon/status/379823208305655808

On a parting note, Dana Loesch points out that an "AR-15 style shotgun" still isn't an "AR-15 shotgun."

https://twitter.com/DLoesch/status/379807018359332864