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; 92FS; 92S; 8040G | RIA GI 1911 | Sig Sauer SP2022; P6 | Colt Python 4"; 1968 Detective Special 2"| Smith & Wesson M642 No-Lock | Ruger LCP | Daniel Defense M4V1 | Alpine M1 Carbine | Steyr M1895 | Ruger 10/22 |1943 Mosin M91/30 | Remington 870