Mike McQueary Testifies -- I'm Not 100% Sure Sandusky Was Raping That Boy

Mike McQueary says he's not 100% positive Jerry Sandusky was anally raping a young boy in a Penn State shower back in 2002 ... but he's CERTAIN Sandusky was sexually molesting the child.

McQueary -- a Penn State assistant coach -- took the stand in a preliminary hearing for 2 former PSU officials this morning, and said he became suspicious when he heard skin-on-skin slapping sounds coming from one of the showers.

McQueary says he peeked into the shower and personally saw Jerry and the boy naked in the shower together -- with Jerry grabbing the boy's waist from behind, while the boy was facing the wall.

McQueary says he peeked in the shower several times -- and by the last time, they had separated. But McQueary told the court, "I know they saw me. They looked directly in my eye, both of them."

"Seeing that they were separated, I thought it was best that I leave the locker room," he explained.

McQueary says he went to Penn State football coach Joe Paterno to report the incident the following morning -- but didn't use the words "sodomy" or "anal intercourse."

McQueary says Paterno slumped back in his chair and appeared disappointed, but told Mike he had "done the right thing."

When asked why he didn't report the incident to police, McQueary explained that he had spoken with PSU Vice President Gary Schultz and felt that was good enough because Schultz oversaw the campus police.