"As soon as United States Air Force investigators stationed at Kunsan Air Base were made aware of the incidents, they, with Korean National Police, immediately and aggressively investigated the allegations, and Kelgard was militarily prosecuted for his crimes," the commander said.

"This is a very shameful past moment for Kunsan Air Base and our community," he added, stressing that the crimes by the "predator" are not reflective of US service members who serve here for the defense of South Korea under an alliance treaty.

In October 2014, Kelgard was put under investigation for an unrelated incident that happened during his stint at Kadena Air Base in Japan. Investigators searched his computer hard drive and discovered at least 41 child pornography videos acquired from the Internet.

This finding expanded the scope of the probe to Kelgard's prior assignments, including the Kunsan Air Base. In cooperation with South Korean police, the Air Force investigators looked into his contact with two South Korean boys.

The authorities then found that Kelgard had "inappropriate sexual contact" with the boys on and off base, the 8th Fighter Wing commander explained. In 2016, he pleaded guilty to possessing child pornography and molesting the victims.

Court documents indicated that the young victims chose not to participate in the proceedings of the military criminal trial. But a social worker's statement on the victims' behalf that demanded justice for the pain they had suffered was instrumental in the sentencing of the assailant, Bosone said.

Following the crimes, the 8th Fighter Wing has taken steps to prevent a recurrence, such as implementing a more intensive background check of all unit personnel who volunteer to spend time with South Korean neighbors outside the base.

All Kunsan Air Base programs that involve individuals under the age of 18 have chaperones that closely monitor their interactions and relationships.

In addition, all 8th Fighter Wing personnel must complete annual Green Dot Training, an interactive training program that teaches airmen to intervene and prevent situations of sexual and domestic violence, abuse and stalking.

"We take all allegations concerning child sexual assault and child pornography very seriously and pledge to fully pursue all appropriate actions," the commander said, noting that "maintaining trust is a priority."

The US currently maintains 28,500 troops in South Korea as a deterrent against North Korean aggression and provocations. (Yonhap)