Apologies, unsure how local you are. The Warhol Bridge (7th Street Bridge) has been closed for months due to construction. The HOV lane entrance to I279 is a block past the Rachel Carson Bridge (9th Street Bridge). The encampments were eliminated in 2015 and the homeless were relocated. There is a fence up there now preventing homeless to set up tents again. In any event, that the 7th Street Bridge is closed, and that Dakota lived in the Parkview Apartments in Allegheny Center, leads us to realize that the Clemente Bridge (6th Street Bridge) makes more sense to walk over to reach home rather than the 9th Street Bridge. The North Side is actually quite a nice area as a whole. Up the hill on the North Side isn't the best area -- Perrysville, Northview Heights, Fineview -- but these neighborhoods are nowhere close to North Shore/ Allegheny Center/ Central Northside.
My opinion is that it would be difficult for a person to fall into the river if the individual was walking over the bridge, but perhaps not so difficult if the person was walking along the trail near 10th Street Bypass. Directly across the 6th Street Bridge is PNC Park (along with the 3 restaurants that are part of the ballpark), 4 separate restaurants/bars, a bank, and 2 hotels. Once you cross the bridge, 6th Street becomes Federal Street which leads to Allegheny Center.
I walk through Allegheny Center on my way to work in downtown every day. I can think of 2 homeless people that I see on a regular basis during my commute and 3 other homeless people I see on occasion. All 5 of these homeless people hang out on both the downtown/cultural district area (as well as the trail along the 10th Street Bypass) and the North Shore. I wonder if the police have spoken with them to ask if they saw anything?