If the buck was still part of some study, the tags and collar should have had all sorts of information on them. If the collars were state collars (depending on state laws), there may be a legal obligation to report its recovery. For example, that is/was the case for state tracking collars for bears in Alaska.
The people that tagged the deer probably expected that it might get shot. They'd be very happy to get their tags and transmitter back along with measurements of the deer.
Right! If a local or university study of some sort, there may be a $ reward for the return of the collar.
I don't know why people would not shoot a tagged animal if it is legal to do so. I would be more inclined to believe they were upset that all their good game was being taken out of play by biologists or "the state" by tagging it like that. They aren't taking the animals out of play by tagging them. In fact, the tags may be part of a mgmt plan tracking hunting pressure and other factors to see how the population is responding.