Call a wildlife place or spca, or release it in a wild wooded area.
There is a very old superstition that once a turtle bites it won't let go until it hears thunder. I'm sure thats where the "it won't release until dead" thought came from. It is nothing more than an old superstition. Trust me, if they didn't let go then I'd have turtle body piercings yet.
Your risk of salmonella from a wild caught turtle is extremely low also.