What would you do ? 1# inside knowledge

What would you do if you had knowledge of some scheme that includes a person getting hurt. I would tell someone who can help stop the unfavorable of this scheme. Lets say one of your best friends were planning to rob someone, and they ask you to help them. Would you help them or would you tell someone? Think of it this way, you have the ability to save a life or take a life. One story that shows these specific circumstances is the story of "Guy Fawkes" he had the idea to eliminate the English government, so he joined a group called the "Flanders" and they were planning to put gunpowder in the cellar of the Parliament. My point is anyone of the Flanders could have chosen to save a life but all of them chose to take one so their lives were taken.