to prohibit the person from entering or remaining in or upon the public or subsidized housing development, unless there is cause to believe that such unlawful conduct is unlikely to continue or to pose a serious threat to the health or safety of the development, the tenant households at such development, or the employees of the landlord. Whenever a tenant or member of a tenant's household residing in a public or subsidized housing development has caused or threatened to cause harm to another tenant, an employee of the landlord, or any other person who is known or believed to be a witness in an eviction against the tenant, the landlord may bring a civil action for injunctive or other appropriate equitable relief in order to protect the witness from harm threatened by the tenant or member of the tenant household.