How can tenants get a property manager fired?

Contact the Federally Subsidized housing main office, and tell them what is going on. They should do an investigation. Usually, they do an interview once a year if these places are getting money from the Government. You may need to go to some type of free/low cost attorney. In California we have something CRLA, California Rural Legal Assistance. Good Luck. What they are doing is so wrong. Other than that your family member could have another deadbolt installed, that they don't have a key to. Also, document everything. Get a video camera, and write down the times/dates, and also call the police to make police reports anytime anything happens.