Whatever he was using.
This.
Other than an SBS, I find shotguns a little too long and cumbersome for home defense. No doubt they would work and are fine choice for many, but just not for me. The AR is the gun I shoot the most and feel the most comfortable with. I can operate it day, night, rain, snow, hunt, etc.
As far as ammo goes. 55gn Speer Gold Dots should do the trick in 5.56 . I keep my 300BLK SBR loaded with Barnes 110 TAC-TX and the 6.8 SBR loaded with XM68GD which is also a Speer bonded bullet when I am not at the range.
IMHO, At the ranges these cats caught hell, it wouldn't matter what was round was in that gun, the wound channel/cavity and tissue damage due to the rounds velocity at what is basically point blank (aka across a kitchen) would be devastating.