Retired Air Force colonel and former prisoner of war John Fer shared a cellblock with Sen. John McCain in Vietnam. "CBS This Morning" co-host John Dickerson spoke with Fer about his reaction to McCain's death and what then-candidate Donald Trump said about the senator on the campaign trail.

JOHN FER: America is going to feel the absence of John McCain. I spent, you know, those months and a couple of years pacing the floor with him back and forth and talking, and I got a very good sense of the depth of John.

JOHN DICKERSON: If you were in Hanoi and you heard somebody running for president said about a captive, "I like heroes who weren't captured," would you believe that they said it?

FER: I think it's really, really sad commentary to say … any American captive who had put his life on the line and risked it for, as John says, a cause greater than himself.

DICKERSON: What was your reaction when you heard Donald Trump had said that?

FER: I couldn't believe it. I couldn't believe somebody would say that about a national hero.

DICKERSON: When you'd see him on TV, and you can't always be in touch with him, what would you think back to?

FER: I saw the John McCain that I knew that was the mixture of seriousness of the moment, but he had almost, had a glimmer of a humor that wanted to come out and say, 'Look this is serious business, but we've got to remember… Don't lose your sense of humor, you know, look on the bright side.' ... When I see him in those interviews, when I see him sitting behind the desk in committee meetings and things like that, that's what I see with John. … I see an exceptionally knowledgeable guy who was able despite – and he had by his own admission, he had lots of setbacks in his public life – he was always able to bounce back. And he was a man.