A small and obviously side point--but since you raise it I will give you an English major answer--you get a gold star. The GA's account was an eye witness and thus first-hand account of what he saw; what Paterno told the AD, and could have told the police, was a first-hand account of his own conversation with the GA, but a second-hand account of what the GA reported. Third-hand, in this case, might refer to what the AD might have reported to the university president if he spoke to him before interviewing the GA directly.