[smsm42]

He tested positive for some chemicals that produce false positive on TSA explosives test, not for explosives. As the original article admits, this is a common occurrence. However, it became very clear very soon that he actually does not have any explosives on him. What were they doing once that was clear?

[T-hawk]

They were trying to catch him for anything they could imagine. Maybe he was the next marathon bomber, coming from a laboratory session. They'd be national heroes, or at the very least they'd make damn damn sure that nobody's ass could be on the line for letting the next marathon bomber slip through TSA.

(What? TSA's job isn't to protect marathons? Silly patriot, do you want to let the terrorists win?)