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 1968 Detective Special .38 Spc. - Ruger LCP .380 ACP - Daniel Defense M4V1 Carbine 5.56x45 - Ruger 10/22 .22LR - Remington 870 Express Tactical 12GA - 1943 Izhevsk Mosin-Nagant M91/30 7.62x54R