Lend a Hand?

You were walking through the park and a middle-aged man waves at you. You wave back but as you pass by feel an electrifying bolt from above. Life in the park carried on; you look back at the man for any reaction but then a scene plays in your head. You see the same man being dragged to a black abyss. His screams of agony tacked onto your memory. He will die in five minutes. Will you tell him? Will find another way to get him off the bench? Or will you leave him to die, as he might not even believe you anyways. What would you do?