OMG was i sobbing at the end of the season finale last night!
I had been staying away from all spoilers most of the second half of the season so I was completely blindsided by what happened.
Never in a million years did I think that Captain Montgomery was one of the bad guys or at least working with them. He sacrificed himself and made it all right before he was killed. His funeral had me sobbing like a fool and then the unimaginable happens, Beckett is gunned down right at the funeral as she was giving her eulogy. Castle tells her that he loves her and then she closes her eyes and the credits start to roll. Talk about sobbing and getting hysterical.
Here is a video clip of that last scene thanks to Stephanie from my Castle group.