I did a program for a church security team last year and prepared a "background" overview of actual lethal incidents at churches over the last decade... the majority were INTRA-faith incidents, involving members of the church, former members or someone in the family of a church member. This may have a psychological affect at the outset of an incident (denial & deliberation phases) that could be significant if the church security team doesn't deal ahead of time with the concept of dealing with a member of the flock.
-RJP