I think this situation was very unfortunate. Most of the time, a mass shooter is a lone wolf and as such, acts alone. It's an easy mistake to make assuming you see only one bad guy. The bad wife was "concealed" and only engaged when the CWP holder went after her husband.
But see this guy was not a mass shooter, he was a cop killer, and the private citizen did not know that. The shooter could have been just somebody off their meds, shooting in the ceiling was not a threat without knowledge of the prior killing. If it was a mass shooter he would not told people to leave and his first shot would have been in an innocent victim instead of the ceiling. The shooters had plenty of time to shoot more civilians, yet they didn't and kept telling people to leave. While they were wrong, very very wrong, it is clear their beef was with government not on the people in general.
However brave the hero was, he is a dead hero that did not need to die. IMO his death was in vain. Had he left the outcome would have been the same. One bullet hardly slowed or deterred the two wackos.
Not trying to disparage the man, just that if his death should do anything it should bring some thought to those who carry how to stay alive, and when to get involved.