How could I bring up security concerns at the church that I attend? I currently attend a church on Sundays, and this church serves as a synagogue on other days of the week.  Currently, there is a bit of security at the entrance, e.g. some security guards in uniform, but they are not police and do not appear to be armed.  We get scanned by metal detectors before entering.

How could I bring up security concerns to this church, say, during coffee hour after the Sunday Service?

Basically, I wonder how prepared they are to counter something like a terrorist attack.

I don't want to offend anyone - how could I inquire about this politely?
Uniformed security at a church is uncommon enough that you can use it as a conversation opener.

If I were you I would seek out a (non-clergy) trustee / deacon / elder / congregation-council member / whatever and simply ask "what's up with the guards?"  That should open the topic, and you will likely learn something about the congregation's history and struggles.

How do you find the person to talk to if you don't already know them? Easy: ask a person who serves coffee for an introduction. 

Believe me: asking polite questions of lay leaders honors their offices; they'll love it. Don't hesitate.