Aggression can arise in the middle stages of Alzheimer's Disease. It can be abusive language or even take the form of physical violence. It can happen suddenly and seem unprovoked. It can be frightening to the care provider as much as it it is to the Alzheimer's patient.
First, a reminder: This is the disease talking. If the behavior seems out of character for the Alzheimer's patient; it is. Just remember that their brain is being actively damaged and that damage will manifest itself in unexpected ways.
Second, a caution: Seek help if an Alzheimer's patient you are with or caring for becomes violent. No care provider needs to just accept a beating from an Alzheimer's patient just because it is the disease talking. The care provider deserves safety and an environment without fear. Honestly, it is OK to call the police if an Alzheimer's patient hits you.
The Alzheimer's patient that becomes aggressive or violent needs to be evaluated by professionals experienced with Alzheimer's care. The patient's aggression may be a result of unmitigated physical pain such as from a urinary tract infection. The aggression may be an indicator that the person needs mood stabilizing medications to help them feel calmer or safer. Even if a specific cause is not found, steps can be taken to make the patient more at ease and that helps increase safety for the care provider.