GREYTOWN, South Africa (AP) -- The words of little children from an isolated town in rural South Africa may have stopped an international sex predator.

U.S. investigators say Jesse Osmun confessed that as a Peace Corps volunteer, he for months sexually molested at least five girls at a South African shelter for AIDS orphans and other children. None of the girls were older than 6.

In a Twitter account and blogs, Osmun portrayed himself as a champion of Africa and wrote about working with children. Before coming to South Africa, where he started work at the shelter in March 2010, Osmun volunteered at an orphanage in Kenya, where the director said he did no harm. Osmun also wrote of seeking other international aid work before his arrest last week.

His do-gooder identity may have helped cover a darker side. Then the little girls spoke.

"They were frightened. They were brave to tell. They did something very important," said Samkele Mhlongo, a Greytown police translator who helped an American investigator interview two of the victims from the Umvoti AIDS Centre where Osmun volunteered.

Mhlongo said the children, shown pictures of Osmun, said they described being instructed by him to perform oral sex, and afterward being given candy and warnings not to tell anyone what had happened. Mhlongo said Osmun showed the children child pornography stored on his computer.

According to an investigator's affidavit submitted to the Connecticut court that will try Osmun, a teacher saw Osmun follow three girls into a building at Umvoti on May 24. The teacher followed after a few minutes, and saw Osmun with his back to her, one of the girls near him. Osmun appeared startled and zipped up his pants. A girl later told the teacher about being asked to perform oral sex.

Two days later, according to the affidavit, Osmun was confronted by an Umvoti manager. The same day, Osmun informed Peace Corps he wanted to end his service several months short of the usual two years. At this point, no one told Peace Corps of the molestation concerns. Greytown police told The Associated Press they never received a complaint from Umvoti.

The U.S. investigator said Umvoti's director told her she had confronted Osmun before he went to Peace Corps to ask to cut short his service. She said she had told him she believed he was a child molester and urged him to get help. Osmun told the director he would seek help. The U.S. investigator also said children at the center had come to Umvoti officials with disturbing stories about Osmun months before May. Umvoti officials refused to comment for this article.

Osmun flew out of South Africa June 1, and it was only on June 7 that Umvoti informed Peace Corps of its concerns, U.S. investigators said. Peace Corps immediately sent its own investigator to Greytown, and South African police were informed.

On Aug. 4, U.S. investigators said, they confronted Osmun in Connecticut and obtained his written confession.

Joan van Niekerk of Childline South Africa, which campaigns against child abuse, said that the man the children described to officials fit the profile of a calculating pedophile. Pedophiles seek out places where children are vulnerable, she said, which very much describes developing countries like South Africa, where law enforcement can be weak and awareness of how to protect children low.

Commonly in South Africa, she said, "cases can take years to come to court - during which evidence is lost, contaminated ... and the longer the case takes the more likely the acquittal."

Marita Rademeyer, a South African psychologist who counsels children who have been abused, said South African studies show only one in nine reported cases of child abuse go to court, and when there are convictions, sentences rarely approach the 30 years Osmun faces in the U.S. She said many cases are never reported because victims feel ashamed, or have no one they can trust to tell.

According to South African police, more than 27,000 cases of sexual offenses against children were reported last year, accounting for nearly half of all crimes against children. Experts say the weakness of the South African family - a legacy of apartheid when laws forced adults to seek work far from home - and high rates of crime and violence make children here particularly vulnerable. In addition, South Africa, the country with the most people living with HIV in the world, has millions of AIDS orphans.

Sister Mary Owens, director of the Nyumbani Children's Home, said Osmun volunteered in 2006 at her Nairobi, Kenya shelter for children orphaned by AIDS and children who are HIV-positive. Owens, informed by the AP of the charges against Osmun, said she had spoken with staff and determined he had not been suspected of similar activities there.

Asked whether U.S. prosecutors were investigating whether Osmun had abused children in Kenya, Laura Sweeney, a U.S. Justice Department spokeswoman familiar with his case, said she could not comment.

Osmun had written on a blog of having worked at the Kenyan orphanage, though he said it was in 2004.

The Peace Corps, a 50-year-old humanitarian agency that gives ordinary Americans opportunities to do international development work, said every applicant undergoes a criminal background check and is "screened for suitability."

Liz Hughes, director of South African programs for the international aid agency Save the Children, said such screening is only the first step. Organizations helping children must recognize that people who want to hurt children will be drawn to their shelters and schools, and must train staff to recognize danger signals. Children must also feel confident that when they report abuse, they will be taken seriously, Hughes said.

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