The South Korean student who shot and killed 32 people at a U.S. university was a worry to his family as he didn't talk much as a child, his uncle said Thursday, as dozens of South Koreans held a church service to mourn those slain.

Cho Seung-hui left South Korea with his family in 1992 to seek a better life in the United States, Cho's uncle — his mother's younger brother — told The Associated Press in a telephone interview. Cho killed himself along with students and teachers at Virginia Tech in the deadliest shooting rampage in U.S. history.

Cho "didn't talk much when he was young. He was very quiet, but he didn't display any peculiarities to suggest he may have problems," said the uncle, who requested to be identified only by his last name, Kim. "We were concerned about him being too quiet and encouraged him to talk more."

Kim, who said he was in his mid-50s, said he could not recognize Cho when his picture was shown on television because Cho's family had not visited South Korea since they left 15 years ago.

"I am devastated," Kim said between heavy sighs. "I don't know what I can tell the victims' families and the U.S. citizens. I sincerely apologize ... as a family member."

Kim said his sister occasionally called, around holidays, but had never mentioned having any problems with Cho.

"She said the children were studying well. She didn't seem worried about her children at all," Kim told AP. "She just talked about how hard she had to work to make a living, to support the children."

Kim said Cho's parents ran a small used-book store before they left for the U.S., where they hoped to make a better living and provide Cho and his sister with a better education.

"They had trouble making ends meet in Korea. The book store they had didn't turn much profit," Kim said. He said he has been unable to reach Cho's mother since the massacre.

Cho's maternal grandfather also told local newspapers that relatives were concerned about Cho not talking much as a child.

Cho "troubled his parents a lot when he was young because he couldn't speak well, but was well-behaved," the grandfather, who was identified by only his last name Kim, told the Dong-a Ilbo daily.

In a separate interview with the Hankyoreh newspaper, Kim, 81, said the relatives were worried that Cho might even be mute.

Meanwhile, South Koreans mourned the deaths of those killed at a special church service Thursday, some fighting back tears from the guilt that a fellow South Korean was responsible for the massacre.

About 130 people gathered at Myeongdong Cathedral in central Seoul, casting their heads low as they sang hymns and prayed for the souls of those killed. A small table adorned with white flowers, candles and a U.S. flag was set up in the center of the chapel in memory of the victims.

"As a mother myself, my heart really aches as if it happened to my own children," said Bang Myung-lan, a 48-year-old housewife, holding back tears. "As a Korean, I am deeply sorry for the deceased."

"Among the 32 killed were bright students who could have contributed greatly to society, and it's a big loss for all of us," Cardinal Nicolas Cheong Jin-suk told parishioners. "As a South Korean, I can't help feeling apologetic about how a Korean man caused such a shocking incident."

The cardinal said everyone should work together to prevent a recurrence of "such an unfortunate event."

"It is beyond my understanding how such a thing can occur — especially to think a Korean is responsible for this," said 68-year-old Lee Chun-ja after the service. "It really tears my heart. Something like this should never happen again."

In an editorial, the Hankyoreh newspaper wrote Thursday that Cho's case illustrated a problem faced by many South Korean immigrants in the U.S., where parents are too busy at work to take care of their children.

"It is the reality of our immigrants that parents are so busy making a living that it's not easy for them to have dialogue with young children," the newspaper wrote.

"We should think about whether our society or our (Korean) community abroad has been negligent in preventing conditions that could lead to such an aberration," it said.