SEOUL, South Korea (AP) -- Like most North Koreans, Son Jong Nam knew next to nothing about Christianity when he fled to neighboring China in 1998.
Eleven years later, he died back in North Korea in prison, reportedly tortured to death for trying to spread the Gospel in his native land, armed with 20 bibles and 10 cassette tapes of hymns. He was 50.
His story, pieced together by his younger brother, a defector who lives in South Korea, sheds light on a little-discussed practice: the sending back of North Korean converts to evangelize in their home country -- a risky move, but one of the few ways to penetrate a country that bars most citizens from outside TV or radio and the Internet.
Little is known about the practice, believed to have started in the late 1990s. Missionaries won't say how many defectors they have sent back, citing their safety and that of the defectors.
''It's their country, where people speak the same language. They know where to go and where to escape,'' says the Rev. Isaac Lee, a Korean-American missionary in Seoul who has dedicated his life to spreading Christianity in the North. ''But I agonize a lot whenever I have to send defectors to the North as I know what kind of punishment they would get if arrested.''
Officially, North Korea guarantees freedom of religion for its 24 million people. In practice, authorities crack down on Christians, who are seen as a Western-influenced threat to the government. The distribution of bibles and secret prayer services can mean banishment to a labor camp or execution, defectors say.
For North Koreans, a personality cult surrounding the country's founder Kim Il Sung and his son and current leader Kim Jong Il serves as a virtual state religion.
''Kim Jong Il is above the country's law ... and in North Korea what he instructs is like Jesus Christ's words in the Bible,'' says Son Jung-hun, a human rights activist who has become a devout Christian since his brother's death.
It was into this world that Son Jong Nam was born on March 11, 1958.
He served in the presidential security service for 10 years until his discharge as a master sergeant in 1983. In those years, he was ready to dedicate his life to fighting the ''American imperialists,'' his brother says. Son worked at an army-run performing arts center after his discharge.
The first twist in his life came in 1997.
His wife, eight months pregnant at the time, was arrested for allegedly saying Kim Jong Il had ruined the economy and caused a mass famine. Interrogators seeking a confession kicked her in the stomach, forcing her to discharge blood and have a miscarriage, Son's brother says.
Terrified and disillusioned, Son, then 39, fled in January 1998 with his wife and their 6-year-old daughter to the Chinese border town of Yanji. His younger brother had already arrived the previous year, fleeing what he says was a false charge of being involved in the illegal export of strategic items.
Son's wife died of leukemia seven months later.
That's when the next twist came.
Son grew closer to a South Korean missionary, who had talked to him about Christianity and North Korea, while sheltering and feeding him and his family after their arrival in China.
Their meeting was not unusual. South Korea has a large Christian population, and hundreds of South Korean, American and Canadian missionaries work undercover in Chinese towns near the North Korean border, say Seoul-based activists specializing in North Korean human rights issues.
They hide bibles in shipments of food, clothing, bicycles and other aid bound for North Korea. They release balloons imprinted with the Gospel of St. Mark and let winds carry them across the border. They help North Koreans flee and teach them about Christianity. And sometimes they send them back.
One missionary, Korean-American Robert Park, made headlines after he crossed into North Korea last Christmas, shouting that he brought God's love and carrying a letter demanding Kim's resignation. The 26-year-old was arrested and later released in February.
The South Korean missionary who converted Son disguised himself as head of a timber mill. Son's brother never met the missionary; he says his brother wouldn't let him or even reveal his name, because of concerns about the missionary's safety.
After becoming a Christian, Son began helping the missionary try to convert other North Koreans hiding in China.
''My brother said he realized the Kim Jong Il regime is hypocritical, and living in accordance with what the Bible says is what we have to do,'' the younger Son says. ''Christianity can come upon innocent people like my brother so fast.''
In January 2001, Son was arrested by Chinese police for allegedly trying to convert North Korean defectors in China, which bans foreigners from proselytizing. He was deported home in April, where he was detained and tortured, leaving him with a limp, his brother said. He lost about 70 pounds (32 kilograms) in captivity.
''He was beaten in the head with clubs and given electric shocks,'' his brother says, his eyes welling up with tears.
Son was released in 2004 and sneaked across the border to Yanji to see his daughter, who had been left in the care of a Chinese missionary. He soon decided to return to North Korea to proselytize.
''I repeatedly urged him to change his mind, but he told me he has something to do in North Korea,'' says his brother, who was living in Seoul by then but returned to China briefly to see his brother.
Son headed back with the bibles and tapes. Little is known about how he evangelized, though his brother says Son worked at a state-run defense institute and was allowed to travel freely.
It's unclear whether efforts such as Son's have met with much success. Lee, the Seoul-based missionary, claims his Cornerstone Ministries International has 135,000 members in North Korea.
But experts such as Kim Soo-am at the Korea Institute for National Unification in Seoul are skeptical of purported active underground church movements. ''They know they would get severely punished,'' he says, adding that he thinks many North Koreans aren't even aware of religion as an option.
Son was arrested again in January 2006 after police found bibles at his home in the northeastern city of Hoeryong. He was also charged with spying for the United States and South Korea and sentenced to public execution by firing squad.
His brother launched an international campaign to save him. That apparently led his captors to switch to a less public method: torture. ''There are many ways to kill people in North Korea,'' says his brother.
He died in a prison in Pyongyang, the North Korean capital, in December 2008.
''He told me his dream is to build a church at a good Pyongyang location and work as a pastor there,'' his brother says. ''I thought the religious faith completely changed his fate.''
His death went unannounced, at least outside North Korea. It was not until nearly a year later -- when a fellow inmate who had been released managed to call in November 2009 -- that the younger Son learned his brother had died.