"He had no choice," the source said.
Paterno has come under intense scrutiny following the Jerry Sandusky scandal.
We will have more shortly.
Paterno added a statement shortly after the news broke:
STATE COLLEGE, Pa., Nov. 9, 2011 /PRNewswire/ -- I am absolutely devastated by the developments in this case. I grieve for the children and their families, and I pray for their comfort and relief. I have come to work every day for the last 61 years with one clear goal in mind: To serve the best interests of this university and the young men who have been entrusted to my care. I have the same goal today.
That's why I have decided to announce my retirement effective at the end of this season. At this moment the Board of Trustees should not spend a single minute discussing my status. They have far more important matters to address. I want to make this as easy for them as I possibly can.
This is a tragedy. It is one of the great sorrows of my life. With the benefit of hindsight, I wish I had done more.
My goals now are to keep my commitments to my players and staff and finish the season with dignity and determination. And then I will spend the rest of my life doing everything I can to help this University.