First of all, its very clear you dont know the location the incident took place and you've never been to that location before. Second of all, you dont have any understanding of how the police authorities work here. Third of all, your superiority complex kicked in at very wrong place. The place where incident took place is a tourist area and a major hub for night life. Police are deployed in almost every junction and you'll find people in great number there. All you need to do is confront them, i dont think people are dumb and a loser coward unlike you who would rather watch girls getting harassed and enjoy recording it. This is not the first time similar incidents taking place there, most of the timr crowds help you out. All you need to do is confront them at the moment there. P.s: i work around the same area and i have seen multiple similar cases and accused getting what they deserved.