When to worry?

I was waiting for the subway the other day at rush hour (which I normally do not do, I am fortunate and walk to work) and noticed quite a few police officers on the platform. Then, when the train came, they poked their heads in the car, looked around and remained on the platform.

My friend assured me this was normal, especially at Grand Central at rush hour. However, it raised a question in my mind- when do you start to worry?

Are cops on the platform something to be alarmed about? How about cop cars on my street? That doesn't happen very often, usually only when something big is going on at the UN, but when do I pay more attention?

I know my mom won't watch NY "tragedy" movies (like Pelham 1,2,3 about hostages on the subway) because it makes her nervous. But as I once told my sister, New York City is always getting destroyed, attacked, etc in the movies; you become slightly unfazed.

The police by the subway didn't alarm me because they weren't searching bags, getting on the train, or radio-ing to anyone. So, I guess those actions would make me nervous.

I also have faith that if something happens and I'm trapped in it, then God must have included that in the plan. But it is good to be aware and to not just assume I'm safe.