SIERRA VISTA, Ariz. (AP) — A civilian who held sensitive positions with the U.S. Army in Arizona and Afghanistan led a child sex abuse ring that involved his own adopted son.

An Associated Press investigation finds that the U.S. Army and the state of Arizona missed or ignored multiple red flags over more than a decade.

That allowed David Frodsham to allegedly abuse his adopted son and other children for years, all the while putting national security at risk.

Frodsham is serving a 17-year sentence on sex abuse charges.

One of his adopted sons filed a lawsuit Tuesday, joining two other sons who have filed separate lawsuits against the state for licensing foster parents in a home where they say they were physically and sexually abused.