reporter: many of mccullin's most striking images are now on exhibit at the howard greenberg gallery in new york city vietnam many times. in 1968 to cover one of the longest infantry battles of the war, the brutal fight for whey. his photo of a shell-shocked marine would become one of his most famous. how many images did you take of him? >> five. >> reporter: just five? >> five. i just went click, click, click, click, and the man never batted an eyelid. >> reporter: he also covered the war and famine in beafra. >> allied units -- >> reporter: and the conflict in cambodia. you were almost kill friday cambodia -- killed in cambodia. >> i walked into an ambush. >> reporter: he was put in this truck with the injured. you almost died. >> the man who is dying is dying at the moment i took that picture. >> reporter: as you take this picture, you're wounded. >> but i'm only wounded in the legs. i'm not dying. >> reporter: you're still taking pictures -- >> i think it took my mind away. i thought this is an opportunity to show yet another phase of suffering and war. >> reporter: mccullin's empathy came from h