Human prey ... that's what I'm thinking. Long, hot days make it seem easier.
I agree that the entire area of Bremer County and beyond should be wary until this is solved ... there was a link in the Jessica Ridgeway thread about whether predators tend to hunt closer, or further away, to/from home over time, . Maybe someone recalls the link ... I think stats. showed that predators hunt further away from home as they build confidence.
He could be someone that went hunting in the 7 Bridges Park area as a child, partied on Maiden Lane in high school, assaulted boys in the early 80s, tried to stop, went to 7 Bridges Park as a young adult possibly with family or friends for activities, may even have stopped being a predator of random children for even a couple of decades (see BTK) ... could be in his early 50s, still hunts in 7 Bridges Park, still lives in Evansdale.