What happens when a "Power of Attorney" takes access of the principal's properties before they die?

Could you elaborate on what's involved with "taking access"? Is someone physically taking control of assets, such as moving in, taking furniture, possessions, etc., or is someone "taking access" by selling assets?

A power of Attorney is only valid while the grantor is alive. If the person granted power of Attorney is still competent and are unhappy with actions of the current poa, they can appoint someone else.