I've seen speculation online that there could have been more to it, with the photo being a public tip off. Since the Captain didn't put the scope on himself, and there were surely people running the range there were many chances for people to intervene and they didn't. The speculation is that could be the sign of an unhealthy command culture where people were either so demotivated they didn't care or so actively against the Captain that they did this. Adding to the final buck stopping that the Captain himself didn't notice anything wrong with what should have been obvious.