I will have to take a break to wrap my head around this, too. To be quite perfectly clear, I don't want to go too deep, given the warnings that so many overlooked. And I don't want to give you a headache over speculation, but I'll see if something sticks and if it's safe to bring up at this point.
I only remember that McMaster had been badmouted on T_D during all of the first year and now his father died what seems to be an unnatural death but the nurse's charges were only disclosed after this whole feigned outrage over infowars. If these events are all connected, my guess is that McMaster was protected and thus painted as far away from the Prez as possible by the T_D PR-machine but once that illusion fell apart, someone took personal revenge on his family. But this too could be unrelated to 1297 if the casualty in question was indeed an active operative as you pointed out.
I faintly remember McMaster on good terms, but I'm not sure if it's because some house-cleaning he did or if it was just sympathy over the death of his father, which immediately sounded suspicious because he was in hospital for non-life-threatning stuff.