Watching people die is really not the nicest thing in the world. To talk to someone and to hear their last breath and feel the emptyness of a once full of life person/animal. I know how some of the shots he took must have impacted on him but thanks to these selfless people, the rest of the world gets to know the truth. It takes a special person to come face to face with death whilst working.
http://www.bjp-online.com/british-journal-of-photography/interview/2291888/don-mccullin-i-could-have-gone-on-photographing-wars-all-my-life-but-what-kind-of-person-would-it-have-made-me
This is a repost on BJP, so it may have been linked from here before, but, I really couldn't be arsed with searching ;)