One guy being annoying I can deal with. The time a strange guy followed me about a mile trying to convince me he was a rock star, I just had a funny story to tell later.
Two guys I don't know following me would make me nervous, though, you're right. Just be a good citizen and call the police if you see a situation that looks like it might really be dangerous for someone. That's more than a lot of people do, because people tend to assume someone else will have already done it, or that if everyone else is standing around doing nothing, there must not really be anything wrong.
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-Ugly Duckling the NUT (Neuro-usually-typical)