As many as six assistant coaches at Penn State witnessed "inappropriate behavior" between Jerry Sandusky and boys, stretching as far back as the 1970s, NBC News has learned.
It is unclear if any of the men reported what they saw to higher-ups at Penn State before the sex-abuse scandal erupted in 2011.
The information, which comes from court documents and multiple sources with direct knowledge of legal proceedings, raises new questions about how long the abuse went on, why no one stopped it and whether there could be even more victims than previously known.
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A lawyer for one of the three '90s coaches denied his client had seen anything. A second coach declined to comment. A third could not be reached, and the name of the fourth was not disclosed to NBC News.