Dario Gabbai, a Jewish slave laborer forced to perform as a Sonderkommando at Auschwitz Birkenau under threat of execution by the Nazis, died March 25 at a residence in Los Angeles. He was 97.

He described his grim work at the concentration camp in a series of Holocaust documentaries, including The Last Days, which won an Academy Award for best documentary in 1999, and also Auschwitz: The Final Witness in 2000.

“I have inside some stuff I can never tell,” Mr. Gabbai said in 2015. “I saw so many things. Even now, I like to cry to get it out of my system. But it doesn’t go out.”