If it was really bothering me all that much I would call the cops and give his description. I would say that you had a run in with him and he smelled like whiskey and was threatening to beat you up for whatever reason. If the cops happen to find him and match the description they would have probable cause to get his ID and check him out. If everything came back clean then he was on the up and up, no harm no foul. On the other hand maybe he was riding a stolen bike and you helped catch him.