"Is she alive or dead?"
Donnelly asks the doctor if the woman who had her head shot off is alive or dead. The doctor's reply is simply that she had her head shot off.
"Listen, I'm not defendin' ya no more. I've got my own troubles."
Donnelly draws the line with the Kid. He's helped resolve the conflict the Kid's caused with the Man and Woman on the train, but he's had enough and he can't be in the middle of this young man's pettiness any longer.
"Do I know you from somewhere?"
The Chief Guard asks this of the Kid before he exits the train after interviewing him and Donnelly about the Woman's suicide. We learn that the Kid is wanted for the murder of his mother; it's only after the train pulls out that the Guard remembers how he knows the Kid.