Law prevents the OP from just shooting the bastard, and rightly so. We surrender whatever right we may have to fight and kill on own our behalf, in return for protection from others and enforcement of just outcomes. The point is to remove our personal biases from interpretation of "just".
But if the sovereign jurisdiction won't allow this guy to fire someone who has done this, then its "law" has departed from its proper functions and can't be relied upon. I don't know what it is doing, but it isn't overseeing justice. I wouldn't wait to find out how it goes wrong next. I'd just leave.