If I saw a person stealing someone else's engagement ring, I would stop that person and grab a police officer. I have never witnessed someone stealing before, but that does not mean I should just let it slide. For fear of getting hurt or possibly shot, I may hesitate to speak up. I would first question the person on what they are doing to see how they would respond. It would be either surprised that I saw them or furious. Depending on which reaction I would get, I would either talk them down or call police to step in.