Use your judgment.
Your example is easy, but there are other more profound ones I was thinking of.
You bust a couple of Saudi students who have overstayed their visas and were trying to find flight schools that would teach them to fly an airliner, but wasn't interested in landings.
You bust a kid from Connecticut who tried to break into his mother's gun safe.
You bust a couple of kids in Boston who happen to have pressure cookers in their bedrooms.
You stopped three mass murders, but because you stopped them you never know how horrific the tragedies would have been.
Why would be busting anybody? You can only react to an active threat. Only hindsight is 20/20.