(CNN) -- A judge sentenced a former Peace Corps volunteer to 15 years in prison for abusing girls under the age of 6 in South Africa while he was a volunteer there, federal officials said.

The sentencing was announced Thursday in a statement from U.S. Immigration and Customs Enforcement.

Jesse Osmun, 33, of Milford, Connecticut, joined the Peace Corps in 2010 and worked in a nongovernmental organization's AIDS center for children whose families had suffered or died from the disease, his attorney, Richard Meehan, Jr., told CNN Thursday. Osmun volunteered as a Web designer for the center and worked with older children in a "scout" program.

While there, Osmun engaged in sexual acts with four girls, all under the age of 6, officials said. One girl was abused twice a week over the course of approximately five months, authorities said.

"The way that the government has framed the case is that a teacher walked into a room that (Osmun) was in with three little girls," Meehan said. The teacher noticed that Osmun quickly zipped his pants and, after questioning one of the girls, the teacher found that he had exposed himself and asked them to touch him.

When the program director of the NGO confronted him with these allegations, Osmun confessed to being involved with the four little girls, saying that he had touched them and asked them to touch him in exchange for candy, his attorney said. Osmun resigned from the Peace Corps and returned to the United States.

The U.S. Peace Corps has called Osmun's acts "reprehensible." The organization was notified about the allegations against him after he returned to the United States, and it immediately contacted authorities, the Peace Corps said in a statement.

Special agents from ICE's Homeland Security Investigations (HSI) directorate then worked with members of the South African Police Service and Directorate for Priority Crime Investigation to launch an investigation that resulted in Osmun's arrest on August 4, 2011, officials said.

Osmun was sentenced Wednesday to 180 months in a U.S. prison, followed by 10 years of supervised release.

David Fein, U.S. attorney for the District of Connecticut, congratulated all investigative parties in a statement. "Their collaborative efforts, and this strict sentence, have stopped this child predator," he said.

The Peace Corps donated $20,000 to a fund that Osmun's family started for his victims. "The Peace Corps is committed to ensuring that the children affected by these crimes receive proper care and treatment," Peace Corps Director Aaron Williams said.

"As this sentence clearly demonstrates, there will be no refuge for U.S. citizens who believe that they may victimize children outside the United States," said Peter Vincent, director of HSI's Office of International Affairs. "No place is too distant or too remote to escape the attention of law enforcement."

Osmun's attorney noted that his client gave a full confession and cooperated with the court to spare the victims the trauma of a trial. Meehan attributed these actions to the judge giving Osmun a lower sentence than was recommended.