This man is not a responsible gun owner or man who was defending his life (except at the very start). He acted out cold-blooded murder when the threat was already neutralized.
It is in the interest of gun rights and of basic human morality to condemn what he did. If what we know so far is true, he should never leave a cell again.
That said, innocent until proven guilty.
Beretta PX4 .40 S&W | Beretta 92FS 9x19 Para | Rock Island Armory GI 1911 .45 ACP | Colt Python 4" .357 Magnum | Colt 1968 Det. Spec. .38 Spc. | Ruger LCP .380 ACP | Daniel Defense M4V1 5.56x45 | Alpine M1 Carbine .30 | Steyr M1895 8x56 | Ruger 10/22 .22LR |1943 Izhevsk Mosin-Nagant M91/30 7.62x54R | Remington 870 12GA