Or maybe you find a pipe bomb in a crowded area and decide to alert the police & help evacuate the area. Nothing could go wrong there, you're only trying to save lives. Much like the above posited scenario, how could anyone see you as anything other than a hero?

Look, I'll admit I'm biased (I'm a criminal defense attorney.) That said, you never know which good, wholesome, moral conversation that you have with the police will turn you from a heroic savior into a criminal suspect.

(For what it's worth, I'd speak to the police in your scenario. That said, I wouldn't fault anyone for not doing so.)