There are some theories that can help explain why individuals with Alzheimer's disease exhibit behaviors.  It is advisable to first consult with a physician, who might be able to explain why this individual is exhibiting aggressive outbursts.  The physician may also rule out other medical explanations or adjust any current medications, which might decrease the behavior. 

People with Alzheimer's disease tend to experience confusion and disorientation, which can influence their perception of reality. If their judgment is impaired, they may have trouble distinguishing right from wrong, and it's not uncommon for them to take their aggression out on even the closest family members.  The person may not have control over this behavior, and is likely to even forget minutes after an outburst. The confusion can manifest in many ways, such as wrongly identifying a family or friend.  For example, a woman with Alzheimer's disease may not recognize her husband of 50 years, but approaches her son with the same love and affection she would for her husband.  This may be because her son now resembles her husband from years ago and she cannot distinguish the difference.  In similar ways, the person who you are referring to, might attack their caregiver because they no longer recognize them, or negatively associate them with someone from their past.

It is important for caregivers to remember that the individual has a disease of the brain that may cause them to act differently, which can sometimes be heartbreaking and distressing.  Try not to take these outbursts personally and to continue providing the same unconditional love and affection.  

Assess the situation to protect yourself and the individual with the disease. Should an individual's aggression become violent or physically dangerous, it is essential to always assure safety for yourself and the individual.  Remaining calm while also providing reassurance can help the aggression subside in the hope to regain everyone's composure.