A "younger friend" of my dad's talked him into signing a legal document that gives him easement for his lifetime to the property. What can I do?

My father was very sick at the time this was done. My mother did not even read the document nor did my father. Dad told Mom it was until dad died that Jay had hunting privileges however Jay has it written so that he has privileges until he himself dies. This sets him up to have access to our property long after Mom and Dad are gone and creates the situation where no one will wish to buy the property therefore setting him up to be the no bid buyer.