I think you are a little unclear about Alzheimer's disease versus senile dementia. Here are some links that might help you understand aggression in Alzheimer's disease.
Aggression and Anger
http://www.alz.org/care/alzheimers-dementia-aggression-anger.asp
Aggressive behaviors may be verbal or physical. They can occur suddenly, with no apparent reason, or result from a frustrating situation. While aggression can be hard to cope with, understanding that the person with Alzheimer's or dementia is not acting this way on purpose can help. 
Read more: http://www.alz.org/care/alzheimers-dementia-aggression-anger.asp#ixzz4B00ZWmA1
https://www.alzheimers.org.uk/site/scripts/documents_info.php?documentID=96
Aggression may be linked to the person's personality and behaviour before they developed dementia. However, people who have never been aggressive before may also develop this type of behaviour.