The Bystander effect, someone else will do something, it's someone else's problem.
I may have mentioned this before. In Virginia you can't carry a gun into a church. Several years ago we had a pretty disheveled homeless looking guy walk in to church carrying a backpack one Sunday and make his way towards the front of the Church.
I always carry my Leatherman with me and while it is not much it is better than nothing. I made quick survey of the situation and told my wife that if I stand up she is to get under the pew and stay there until I come and get her.
The ushers managed to get him out with out an incident and he was just looking for a handout, but you have to stay vigilant no matter where you are.
:: The Bystander effect ::
I think it is worse than that. We have been trained [by our benevolent overlords] that only the police can take of the situation so it is better to do nothing. Wait for them and things will be OK.
And BTW, what do churches in VA think about the State making rules for them in light of the 2nd Amendment?