Maybe none; maybe being heavily armed in public in MA is a violation. At any rate, a cop thought they might be suspicious, doing his job, asked them for ID and they ran. It follows that further inquiry is indicated, which is what happened. But first, of course, they have to be asked again, thus necessitating their temporary detention. If the government is entitled to spy on unarmed TV journalists, then one suspects they might be given a bit of latitude to inquire about this group. Agree?
To demand ID requires reasonable suspicion of a specific crime. Just ‘suspicious’ isn’t enough.
These guys may be up to no good. They may be just exercising their rights - but until law enforcement can site the statute where a law is being broken they have no authority. Otherwise they’re just fishing for crimes and violating the 4A.