A recent article in the New York Times reports on the problem in assisted living dementia care facilities of residents physically attacking other residents.  The estimate is that 8% of such residents are victims of these attacks.  The necessity for vetting prospective residents and for removing aggressive ones is evidenced by a recent jury award of $1.9M to the family of a woman resident who was attacked by a male resident.  He threw her to the floor and broke her hip.  While the ALF said that the man was a friendly resident,  it turned out that he had been violent with the staff and other residents, and in fact his wife had brought him to the ALF because she was tired of his violent behavior.  When the woman resident returned to the ALF,  she was so weak she fell again, and died shortly thereafter. 

Staffing sufficiently for supervision is one way of lessening the danger.  Another is—as stated—a solid vetting process for admission.  In any event, if a problem arises,  it is imperative to resolve it immediately, and be honest in reporting to the family what occurred.