Well, when told it was "inappropriate" conduct in the shower between a grown man and a child, he concluded it was sexual in nature, pretty much anyone would, but what is most damning, was that he did NOT ask McQuarry what he specifically saw, and showed, no curiosity or interest in the details, not at that point in time, nor at any point and time after.
The "don't tell me, I don't want to know" school of thought, may get you a pass on legal grounds, but it will never get you one on moral grounds. He may not be charged, but he will be shamed.