from espn:
"And in 2002, Kelly said, a graduate assistant saw Sandusky sexually assault a naked boy, estimated to be about 10 years old, in a team locker room shower. The grad student and his father reported what he saw to Paterno, who immediately told Curley, prosecutors said.
The two school administrators fielded the complaint from the graduate assistant and from Paterno.
Two people familiar with the investigation confirmed the identity of the graduate assistant as Mike McQueary..."
Penn State Nittany Lions sex abuse case -- Officials arraigned; police seek alleged assault victim - ESPN