The map insets show a dashed-line (representing the train) crossing southward over the bridge. The "first shot" I set at about Z160.
The middle inset (Altgens 07) was taken about two seconds before the Weigman film capture below.
The hypothetical train southbound progression would be about 30 feet further south in Wiegman than in Altgens 07. So such a train would not appear in Wiegman. The Paschall and Daniel films (below) are a bit late and not far enough south.
The film by Malcolm Couch began about 25 seconds after the head shot (or about 33 seconds after my
ca.Z160 "first shot" on the top graphic). The clip showing the policeman with gun drawn and the south area of the bridge is some time later.
In this scenario, the freight might have not been between Officer White and the limousine by Z313, but the noise from it would largely be present, mixing in with and obscuring the last shot. Daniels heard three shots and Mel McIntire heard none.