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Marvin Bochner will never forget the putrid smell in the air as he and the other men in his U.S. Army unit marched toward the Ohrdruf concentration camp on April 4, 1945.

Bochner and his comrades in the 89th Infantry Division had no idea what awaited them inside.

But then they saw them — gaunt, ghostly figures staggering down the roadway. The soldiers were not sure who they were. A few mistook them at first for enemy troops.

Marvin Bochner today at 93 years old. Courtesy Marvin Bochner

"They looked like the walking dead, just skin and bones," Bochner, 93, recalled in a phone interview this week. "But as we got closer, we saw they were wearing a grey-striped uniform."

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He soon learned the truth: They were Jews, just like him. Jews who once led normal lives, with jobs and schools and families — just like him.

"A little boy walked into that camp that day," Bochner told NBC News, referring to himself. "And a bitter man walked out."

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Ohrdruf, part of the Buchenwald network in Germany, was the first Nazi death camp liberated by U.S. troops. And that made Bochner, a native of Brooklyn, one of the first Americans to witness firsthand the horror and depravity of the Holocaust.

Marvin Bochner, apart of the 89th Infantry Division, during WWII. Courtesy Marvin Bochner

He will never forget the lifeless bodies and burnt bones stacked around the camp. He will never forget the emaciated prisoners, too weak to eat. He will never forget the hardened combat infantrymen around him who dabbed at their eyes or broke down in tears or vomited.

Decades later, Bochner's granddaughter asked him why he had never told them about his experiences in the Army.

"I said, 'Look, you were youngsters and I just didn't feel like talking about it,'" he said. "And she asked me if grandma knew. I said, 'Yes, she did, because she spent many a sleepless night with me as I screamed, trying to calm me down.'"

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Bochner, who now lives among Holocaust survivors at an assisted living center in Long Island, has somehow found the resolve to speak openly about the war years. He occasionally lectures to student groups and appears at libraries, helping to ensure that the memory of the Holocaust is never forgotten.

He recalled a recent conversation with a young man who referred to the Holocaust as a "fairy tale."

"I wanted to smack him," Bochner said. "I don't forget what happened. To walk into a place like that ... I don't forget what happened."