There is no right answer here. I wrestled with the carrying in chuch issue spiritually. I was against, and changed my mind. Now I do. However, in a large congregation, Tom is right. The largest danger is the panicked crowd, not whatever caused them to panic. Unless you can be the first out the door, don't go there. Find a place to hide, a confessional, the baptismal font, a small side chaple etc. There, you are safe from the crowd and in reasonable range if the BG does turn that corner. You'll be shooting at 20 feet, not 50 yards, which is what a carry gun (and just assuming here) your level of training is geared for. My advice is to ride it out if you have family. If not, then work your way to the BGs if you want, but understand if you can't make a shot reliably on the range, you sure won't under fire. Again, I really think that your fellow parishoners are the biggest threat odds wise in that scenario.
FQ13