Once upon a time an elderly man was making his way home through the park after a long day at work. Some youths set upon him. They were carrying knives. They mugged him, injured him badly and left him lying in a pool of blood.
A while later a city gent happened to pass by. He looked at the bleeding man on the ground and thought: This may be a trap. If I stop to help him someone might come out from the bushes and attack me. I’d better hurry home.