A good number of mites on the bottom board....
but they may also have simply starved. That cluster is at the top of a frame. I don't see any honey in adjacent cells. If there was a super with honey immediately above they'd still likely not find it. That few inches between the top of one frame and the bottom of another, in cold weather, is all it takes. I'm voting for starvation.
I don't blame the beekeeper....I just found one of my own....its just a bad set of circumstances. How could you ever predict it?
Let me never fall into the vulgar mistake of dreaming that I am persecuted whenever I am contradicted. - Emerson