For Helen Rieder of Tujunga, the terrifying flashbacks come when a woman shouts at her.
For Paula Lebovics of Encino, it's when she hears the sounds of boots or sees men in uniform.
For Vernon Rusheen of Woodland Hills, it's when he takes a train.
All three are Jewish survivors of Auschwitz, the Nazi death camp liberated 50 years today by Russian troops.
A half century later, the most mundane moments in everyday life can still trigger the most terrible memories.
The shouting brings back images of female SS guards who gave orders at the camp. The boots are reminders of German patrols. The trains evoke the daily transports that brought human cargo to Auschwitz.
"I don't remember what happened last week," said Simon Korn, 71, of Studio City, who also survived, "but I do remember Auschwitz. I can smell it. I can see the blades of glass. I can feel when I was kicked."
This week, with events around the world commemorating a landmark anniversary of the camp's liberation, the memories are especially painful. But for the survivors, the anniversary also serves as a reminder that their memories must be shared.
Eventually, the anniversaries will come without survivors to tell their stories.
"It's a changing of the guard," said Marvin Hier, dean of the Simon Wiesenthal Center in Los Angeles, a Holocaust study center. "Memory, from this point on, will belong to the next generation, and I am very concerned about what the meaning of that memory will be."
So is Michelle Korn. For decades, she spoke little about her camp experiences. She didn't want to "burden my children with my pain."
But her husband and children are almost her entire family. Michelle and Simon Korn--who were both in Auschwitz but did not know each other there--lost dozens of relatives in the Holocaust.
As they grew older, the Korns began to speak out.
"When you're older, you miss the family you would have had even more," said Simon Korn. "You're alone, and that's scary. When you're younger, you're busy with life."
For Rusheen, 70, who spent two years at the camp, it was having grandchildren grow up that encouraged him to talk about his experiences after years of near silence.
"I want them to hear the story in person," he said, "because, by the time they grow up, people will have a doubt that the Holocaust ever took place. And they are much stronger to take all this because they have a family of both parents and grandparents. My kids didn't have that."
Rusheen's parents both died in the Holocaust.
Rena Drexler wanted so desperately to forget Auschwitz that after the war she had surgery to remove the identification number tattooed on her arm. The constant nightmares were not so easy to eradicate.
In 1992, she visited the camp for the first time since the liberation in hopes it might help rid her of nightmares. They only got worse.
It was only when she began to pass on her experiences to the younger generation during numerous speaking engagements at local elementary and high schools that her nights became more peaceful.
"It's how I get out all my frustrations and memories," said Drexler, 68, of North Hollywood. "As long as I live, I have to speak about it. It's my duty."
Drexler now regrets that she erased her number.
"I should have treasured it," she said.
Part of the story Drexler tells is the camp's liberation, and how it was not entirely joyous. She was happy to see the Russian troops, but says they treated women prisoners roughly and seemed unsympathetic to what the survivors had endured. They also arrived with little food.
After a few days, along with other ex-inmates, she ran away from the camp and roamed through Eastern Europe, looking for food, shelter and medical attention.
"I was standing on the streets, begging for food," she said. "I didn't know what was going to happen. Where would I go? Was it worth it to be liberated?"
Lebovics has no such doubts. Only 11 when the Russians came, she met a soldier who gave her reason to hope.
"He picked me up, and rocked me in his arms," said Lebovics, now 61. "Tears were flowing down his face. Somebody cared about me. I cannot forget that."
Rieder can't forget the sounds of the trains as they pulled into the camp, the screaming of the arrivals as they were separated from their families, the barking of the German dogs.
And the smell of the smoke that came from the chimneys.
"I remember one night, there was this horrible smell and terrible screaming," she recalled. "We heard later that they had killed 2,000 Gypsies that night."
To this day, Rieder has trouble with crowds because they remind her of the thousands of people being pushed by the Nazi guards. Whenever she finds herself in a new environment, she makes sure to spot the exit. She always tells her husband where she is going.
She cannot abide shouting.
Just last week, a woman started to scream at her over an incident Rieder did not want to describe. Rieder told her to stop, but it did no good. Finally, it was over. The woman never knew the emotions she had awakened.
"I wanted to say," Rieder said, " 'You are not in the Gestapo.' "