The director of the Peace Corps, Aaron S. Williams, announced Tuesday that he is stepping aside after three years on the job.
"This has been a difficult choice because serving in this position has been the highlight of my public service career," he said in his message to colleagues. "It has brought my personal journey in government full circle - from Peace Corps Volunteer to Director. It is time, however, for me to shift my focus to my family."
Williams, who leaves effective September 17, served as a volunteer in the Dominican Republic from 1967 till 1970. He was sworn in to the organization's top job in August 2009 and immediately found himself dealing with security issues related to the volunteers.
Four months earlier, 24-year-old volunteer Kate Puzey had been killed in Benin.
And last year, an ABC News investigation reported that more than 1,000 young Peace Corps volunteers had been sexually assaulted during the prior decade.
Also last year, a Connecticut man pleaded guilty to traveling to South Africa to engage in illicit sexual conduct with children while he was a Peace Corps volunteer there.
At the time, Williams said, "The Peace Corps has no tolerance for abuse of any kind, and our deepest sympathies are with all the victims involved." He vowed that the Corps would ensure that the victims were properly cared for and treated.
In congressional testimony in March 2011, he said, "While the Peace Corps cannot eliminate every risk volunteers face during their service, I am committed to making sure that we do everything we can to protect volunteers and provide effective support to them and their families when a tragedy occurs."
Williams has worked with Congress to codify reforms and increase support to volunteers in the field, including hiring a victim advocate; enhancing safety and security, as well as support and response for volunteers; and improving training for volunteers and staff, the organization said.
In a statement on Tuesday, President Barack Obama credited Williams with having helped "in reforming and modernizing the agency."
Deputy Director Carrie Hessler-Radelet will serve as acting director upon his departure.
In all, more than 9,000 volunteers serve in 75 host countries, according to the Peace Corps. Since its establishment in 1961, more than 200,000 Americans have served.