The problem is cultural. We are solving problems on all sides with guns. In short, we have a gun culture which routinely invades not only houses of worship, but worship itself, along with myriad other aspects of culture such as identity and work.
An armed citizen cannot stop the statistics, only ameliorate a symptom. Importantly, as the armed citizenry comes to the fore, as with any cultural phenomenon, complications multiply and side effects manifest themselves. Armed citizenry is a double edged sword.
The matter is a circle to begin with — arm both sides is the history of the arms industry. The armed citizen reinforces the vicious circle.
The nasty righteous armed folks are responsible. Money is the root of all evil, and gun culture is a certain route to both.