The Department of Natural Resources is not the police. The DNR are in the business of tranquilizing animals, the local police are not. The DNR had a tranquilizer gun, the local PD did not. Black bears are not even close to an endangered species, so the local PD decided that even a slight threat was unacceptable.
I'm not sure about Minnesota, but certainly in most of the west, bears and other large predators were hunted to near extinction through the nineteenth and early part of the twentieth century. The bear on the state flag of California, the Grizzly, was actually exterminated. Hunting was then banned or strictly regulated, allowing populations to recover. Which they have done, to the point that many states are lifting hunting bans, or extending hunting seasons, because excess bears are becoming a nuisance.
If the police chief had waited for a tranquilizer gun to become available, and anyone had been hurt in the slightest because of having to wait for it, he would certainly have lost his job.