You have to look at the lease. Most leases have specific provisions spelling out the circumstances under which the owner can enter the leased premises. The behavior you describe is pretty outrageous, but outrageous may not be enough. It is entirely possible that he violated the lease provision. IN addition, being late on the rent doesn't give the landlord additional rights to bully or harass tenants. If your daughter fears retaliation (you don't say what kind or on what the basis for this fear) then all of the tenants need to consider talking to a lawyer and, then, possibly informing the police of this behavior.