"Once I read the letter and researched on the Internet, I realized that this may be the real deal.
"For people who have never been there, it's impossible to imagine," he said.
"The first thing they do is to take your human dignity away and humiliate you." Zhang recounted the systematic use of beatings, sleep deprivation and torture, especially targeting those like him who refused to repent.
"I hid it in a hollow space in the bed stand -- and only got time to write late at night when everyone else had fallen asleep," he recalled.
"The lights were always on in the camp and there was a man on duty in every room to keep an eye on us." Demonstrating his awkward position in bed, he continued: "I lay on my side with my face toward the wall so he could only see my back.
Released from the labor camp but afraid to be sent back, he agreed to his first television interview on the condition that CNN concealed his identity. Zhang" -- as he would be called -- is a follower of the Falun Gong spiritual movement, branded by the Chinese government as an evil cult and outlawed since 1999.
He claims he was detained by police several months before the 2008 Summer Olympics in Beijing and sentenced to two and a half years in the Masanjia labor camp in northeastern China.
I had no idea if this person was still alive or dead or in the camp -- it's extraordinary that it was able to come all the way from China." China's forced labor camps: One woman's fight for justice Keith heeded the writer's call by reaching out to human rights groups but received no response.
She then posted the letter on Facebook, which prompted the local Oregonian newspaper to run a front-page article.
As word of Keith's unusual Halloween discovery spread, her story turned into international news, throwing a spotlight on one of China's most notorious labor camps -- and the controversial system behind them.
Strange discovery Then one morning recently, some 6,000 miles away from Damascus, a bespectacled middle-aged Chinese man walked into the CNN office in Beijing to talk to us about this strange discovery half a world away.
"Every letter was slightly different because I had to improvise -- I remember writing SOS in some but not in others. I had studied the language but had never practiced speaking or writing much.