As a matter of practicum in the times and days we are in, most Churches have in place a form of security for just such things as this.
At my Church and the two others prior, we made sure the people coming to Church would be safe as possible should some miscreant decide that he wants ten seconds of fame.
We quietly identify any former military, or Law Enforcement who are accustomed to reacting to things like this, and then find out who has all the current licensing to carry and trains at a shooting range.
We have men casully walking the parking lot keeping an eye on things on the outside while on the inside there are at least FOUR armed and loaded people at all 4 corners of the auditorium who will rapidly respond to some wannabe mass killer.
This is very common practice in lots of Churches out of necessity. IFFEN some perp visualizes themselves as a famous mass killer and lots of television time, I know a lot of Churches where theonly fame he is gonna get is having more holes in him than swiss cheese and being dead.
Very happy the man who shot this thug was a good shot but feel very badly for the two people's families and loved onesleft behind who were killed by this perp before he got popped.