MOO BG has the print of a deep grip hand gun like a Glock or 1911 in his right hand pocket.
A gun makes sense of his immediate control in making the girls move.
MOO I don't think the girls would respond to a request for any reason, with or without the color of authority to move off the bridge end to private property without a direct threat.
Gun, knife, fake ID all possible and they all amount to the same thing. I don't think this part of the crime is difficult to understand they were just young girls. I was once walking with my wife along a train track and a man came by and told it was a 10000 fine to walk there and to come with him away from the tracks - we went. He didn't kill us but that is how easy it is.