Government entities are generally immune from lawsuit because of the acts or omissions of their employees. It's a concept called "sovereign immunity". There are exceptions to that rule, but they are very narrow. I don't mean to dissuade you in your search for justice. Just be aware that if you want to pursue his action, you need to be aware that the road is long, hard and costly. And there is a significant chance that you will come out of the matter with nothing.
That being said, in my opinion you should look for an attorney who has experience in suing state and local government.