How do we know when someone like Hasan is going to make his...

How do we know when someone like Hasan is going to make his move and do we know he's an Islamist until he's made his move? He makes a phone call or whatever, according to Reuters right now. Apparently he tried to contact al-Qaida. Is that the point at which you say, "This guy is dangerous?" That's not a crime to call up al-Qaida, is it? Is it? I mean, where do you stop the guy?