Can anger be dementia?

Unreasonable anger, confusion and delusions can also be a sign of a urinary tract infection, especially if the symptoms come on suddenly. But, it’s true that in the early stages of dementia, anger can be caused by realizing you can’t remember how to work the television remote any more.

if at any time the person you are referring to becomes so angry they become a danger to themselves, or anyone else, it’s time to call the doctor or even 911

When a person has dementia, anger is often a stage they go through.

Well Kathy, anger can certainly be part of dementia. Who wouldn’t be angry when dealing with the loss of cognition?
But since you have given little information it’s difficult to know how to offer help.
Consider the meaning of the word.
de·men·tia
a chronic or persistent disorder of the mental processes caused by brain disease or injury and marked by memory disorders, personality changes, and impaired reasoning.