Turns out the guy who shot the gunman was an ex reserve sheriff's deputy, and who owns a commercial gun range. Single shot to the head; best I can guess from the video it was from around 25 feet. First shot to last shot took around 2 seconds. First appearance of the shotgun to last shot was around 4 seconds. From confronting the guy, who had an obviously fake beard and wig, wearing a long coat, to last shot was around 6 seconds. Response time just doesn't get any better, unless they murdered the guy before he showed to be a threat.
Prayers for the congregation and particularly the reserve deputy, who was the real hero that day. It's going to haunt him forever. He's getting by for now with knowing "he killed an evil". There were perhaps 6 other congregants who were armed, so regardless, the gunman wasn't getting far.
Gunman had a misdemeanor deadly conduct beef, and several unpaid tickets. Somewhat of a vagrant. He had been to the church before, and was approached to see if he needed help. This is how he repays that kindness.
Hero used a Sig P229 chambered in .357 Sig.
Pretty good shooting for an incident that just never happens ... until it happens to you.