On April 17, 1975, the Khmer Rouge took over Phnom Penh. It was Mam's 18th birthday. One of 11 brothers and sisters in his family, Mam had no idea the Khmer Rouge movement would escalate the way it did the next four years.

His father and three siblings died in the genocide. Mam says he was one of the lucky ones. He has forgiven the Khmer Rouge because being angry at them would continue a dark cycle. His biggest struggle is understanding who was responsible for the genocide and how Cambodians could kill so many of their own countrymen.

"Once in a while it hits me in the head - Why?" Mam said. "It's a question, but there's no answer."

"I forgive them, but I never forget what I've been through."

Today, Mam lives near Phoenix with one surviving sister, his wife and three children. Memories of the genocide have left Mam with a painful scar, but he says it's important to talk about it so more people are aware.