Who is Father Francis Patrick Xavier Mulrooney from The Dead and the Gone and what is their importance?

Father Francis Patrick Xavier Mulrooney is the new priest at Alex's school. He is called into active service when many of the priests and instructors at the school leave town. Mulrooney is described as an old school priest; upright, proper, and unbending. He is hard on Alex, not because he dislikes him, but rather because he believes Alex is capable of great things.