I have lived in this area my entire life, and I worked as a taxi cab driver for more than 5 years, that placed me at the Other Side, every night, so I am very familiar with the area. You can't see the river from the street, and I've never seen anyone venture back there, aside for a few instances, one where I found a crying woman by the railroad tracks and gave her a ride home, and another when someone was running from the police . The Other Side is on Sinsinawa Avenue, and it has cameras on both ends of the street. Dan was last seen traveling east, which is the way toward the bridge. The camera at the other end of the street does not show him going past. However, a green cab driver, claims Dan was at the Mulgrews at 3:20 AM and was to return at 3:30 AM for pick-up and he was gone when they arrived. The police say the camera doesn't show him entering Mulgrews, so that's strange. There is also cameras on the bridge, which malfunctioned. However, the cameras on the other side of the bridge do not show him exiting the bridge on foot. The map doesn't show the distance and obstacles to the river from this position so I find it highly illogical that he would venture toward the river, because his circumstances would be to return home, based on text messages. Since he didn't cross on foot, he must've gotten into someone's car. We know that he made it back across the bridge because his cellphone last pinged off a tower on the Dubuque side. If they don't have him on camera crossing the bridge, then he must've gotten into someone else's car. It is not uncommon for people to hop in with random strangers to get a ride over the bridge, and the police station is near by the Other Side on the same street, and right across the street from Mulgrews. At bar close, the cops clear out anyone left in the street - anyone left stranded there after the bars close knows they'll get arrested for a public intoxication if they don't have a ride.
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Based on the available evidence, they need to figure out who drove him over the bridge. It would be wise to run plates of all the cars that crossed the bridge around that time and look for something unusual. IMO