Factual error: When the Marines strip off and run into the sea in the final scene, Doc takes off a pair of white socks that would be more appropriate for a final at Wimbledon. Not only are they white rather than khaki, they are virtually spotlessly clean which would be impossible after a week of fighting on the black sands of Iwo Jima.
Factual error: The water is perfectly still around the ships as they bombard the island. When the cannons fires there are small ripples on the water from the shockwave, but around the ship it remains perfectly calm.
Answer: The movie insinuates that he was killed horribly but doesn't provide many details. Books about Iwo Jima have quotes from witnesses about what happened to him and they all say that he was very brutally tortured, including having his eyes cut out and his genitals removed and stuffed in his mouth. The book "Flags of Our Fathers" contains the following quote, "A few days later someone yelled that they'd found him. They called me over because I was a corpsman. The Japanese had pulled him underground and tortured him. His fingernails... his tongue... It was terrible. I've tried hard to forget all this.