“The Colt M16A2 fires a 3-round burst, but that’s not something that a civilian would typically own.”
I understand that. I own an AR-15. It is incapable of firing anything but one round per trigger pull. OTOH the M-16 is capable of full auto or three round bursts. My point was that Griffith was saying that the shooter was using an AR-15 and that they knew that because it was capable of three-round bursts.
Since Sandy Hook, reporters will typically refer to any military style rifle as an M-16, AR-15 or AK-47, it seems.