Our church has had a group who are armed and train together and coordinate inconspicuous monitoring of the church and services every Sunday for several years now. They politely try to engage persons who exhibit suspicious behavior and will sit close to any person of concern and notify others on the team of any concerns. They have had many interesting encounters but none that were a direct threat.

"If you are the smartest person in the room, you're in the wrong room"

"How you do Anything, is how you do Everything"

"It is the mark of an educated mind to be able to entertain a thought without accepting it"